Doctype html public ошибка - Не ошибается лишь тот, кто ничего не делает!

I get the following syntax error in Firebug and I don’t get what’s it:

> syntax error [Break on this error]
> <!DOCTYPE html PUBLIC "-//W3C//DTDXHT...org/TR/xhtml1/DTD/xhtml1-strict.dtd">n

Is it because of the final «n» at the end ?

thanks

ps. I’ve just realized if I remove all scripts, I don’t get that error. For example, if I remove these lines, I don’t get it. If I add another script I get it again, so it doesn’t depend on the script itself.

<script type="text/JavaScript" src="<?php echo $base_url; ?>sites/all/themes/bluemarine/js/main.js"></script>

CODE:

<?php
// $Id: page.tpl.php,v 1.28.2.1 2009/04/30 00:13:31 goba Exp $
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="<?php print $language->language ?>" xml:lang="<?php print $language->language ?>" dir="<?php print $language->dir ?>">
<head>
  <?php print $head ?>
  <title><?php print $head_title ?></title>
  <?php print $styles ?>
  <?php print $scripts ?>
  <script type="text/JavaScript" src="<?php echo $base_url; ?>sites/all/themes/bluemarine/js/main.js"></script>
  <!--<script type="text/JavaScript" src="<?php echo $base_url; ?>sites/all/themes/bluemarine/js/griddy-min.js"></script>
-->

</head>

<body>...

Источник

Living Standard — Last Updated 28 January 2023

1. 13.2 Parsing HTML documents
  1. 13.2.1 Overview of the parsing model
  2. 13.2.2 Parse errors
  3. 13.2.3 The input byte stream
    1. 13.2.3.1 Parsing with a known character encoding
    2. 13.2.3.2 Determining the character encoding
    3. 13.2.3.3 Character encodings
    4. 13.2.3.4 Changing the encoding while parsing
    5. 13.2.3.5 Preprocessing the input stream
  4. 13.2.4 Parse state
    1. 13.2.4.1 The insertion mode
    2. 13.2.4.2 The stack of open elements
    3. 13.2.4.3 The list of active formatting elements
    4. 13.2.4.4 The element pointers
    5. 13.2.4.5 Other parsing state flags
  5. 13.2.5 Tokenization
    1. 13.2.5.1 Data state
    2. 13.2.5.2 RCDATA state
    3. 13.2.5.3 RAWTEXT state
    4. 13.2.5.4 Script data state
    5. 13.2.5.5 PLAINTEXT state
    6. 13.2.5.6 Tag open state
    7. 13.2.5.7 End tag open state
    8. 13.2.5.8 Tag name state
    9. 13.2.5.9 RCDATA less-than sign state
    10. 13.2.5.10 RCDATA end tag open state
    11. 13.2.5.11 RCDATA end tag name state
    12. 13.2.5.12 RAWTEXT less-than sign state
    13. 13.2.5.13 RAWTEXT end tag open state
    14. 13.2.5.14 RAWTEXT end tag name state
    15. 13.2.5.15 Script data less-than sign state
    16. 13.2.5.16 Script data end tag open state
    17. 13.2.5.17 Script data end tag name state
    18. 13.2.5.18 Script data escape start state
    19. 13.2.5.19 Script data escape start dash state
    20. 13.2.5.20 Script data escaped state
    21. 13.2.5.21 Script data escaped dash state
    22. 13.2.5.22 Script data escaped dash dash state
    23. 13.2.5.23 Script data escaped less-than sign state
    24. 13.2.5.24 Script data escaped end tag open state
    25. 13.2.5.25 Script data escaped end tag name state
    26. 13.2.5.26 Script data double escape start state
    27. 13.2.5.27 Script data double escaped state
    28. 13.2.5.28 Script data double escaped dash state
    29. 13.2.5.29 Script data double escaped dash dash state
    30. 13.2.5.30 Script data double escaped less-than sign state
    31. 13.2.5.31 Script data double escape end state
    32. 13.2.5.32 Before attribute name state
    33. 13.2.5.33 Attribute name state
    34. 13.2.5.34 After attribute name state
    35. 13.2.5.35 Before attribute value state
    36. 13.2.5.36 Attribute value (double-quoted) state
    37. 13.2.5.37 Attribute value (single-quoted) state
    38. 13.2.5.38 Attribute value (unquoted) state
    39. 13.2.5.39 After attribute value (quoted) state
    40. 13.2.5.40 Self-closing start tag state
    41. 13.2.5.41 Bogus comment state
    42. 13.2.5.42 Markup declaration open state
    43. 13.2.5.43 Comment start state
    44. 13.2.5.44 Comment start dash state
    45. 13.2.5.45 Comment state
    46. 13.2.5.46 Comment less-than sign state
    47. 13.2.5.47 Comment less-than sign bang state
    48. 13.2.5.48 Comment less-than sign bang dash state
    49. 13.2.5.49 Comment less-than sign bang dash dash state
    50. 13.2.5.50 Comment end dash state
    51. 13.2.5.51 Comment end state
    52. 13.2.5.52 Comment end bang state
    53. 13.2.5.53 DOCTYPE state
    54. 13.2.5.54 Before DOCTYPE name state
    55. 13.2.5.55 DOCTYPE name state
    56. 13.2.5.56 After DOCTYPE name state
    57. 13.2.5.57 After DOCTYPE public keyword state
    58. 13.2.5.58 Before DOCTYPE public identifier state
    59. 13.2.5.59 DOCTYPE public identifier (double-quoted) state
    60. 13.2.5.60 DOCTYPE public identifier (single-quoted) state
    61. 13.2.5.61 After DOCTYPE public identifier state
    62. 13.2.5.62 Between DOCTYPE public and system identifiers state
    63. 13.2.5.63 After DOCTYPE system keyword state
    64. 13.2.5.64 Before DOCTYPE system identifier state
    65. 13.2.5.65 DOCTYPE system identifier (double-quoted) state
    66. 13.2.5.66 DOCTYPE system identifier (single-quoted) state
    67. 13.2.5.67 After DOCTYPE system identifier state
    68. 13.2.5.68 Bogus DOCTYPE state
    69. 13.2.5.69 CDATA section state
    70. 13.2.5.70 CDATA section bracket state
    71. 13.2.5.71 CDATA section end state
    72. 13.2.5.72 Character reference state
    73. 13.2.5.73 Named character reference state
    74. 13.2.5.74 Ambiguous ampersand state
    75. 13.2.5.75 Numeric character reference state
    76. 13.2.5.76 Hexadecimal character reference start state
    77. 13.2.5.77 Decimal character reference start state
    78. 13.2.5.78 Hexadecimal character reference state
    79. 13.2.5.79 Decimal character reference state
    80. 13.2.5.80 Numeric character reference end state
  6. 13.2.6 Tree construction
    1. 13.2.6.1 Creating and inserting nodes
    2. 13.2.6.2 Parsing elements that contain only text
    3. 13.2.6.3 Closing elements that have implied end tags
    4. 13.2.6.4 The rules for parsing tokens in HTML content
      1. 13.2.6.4.1 The «initial» insertion mode
      2. 13.2.6.4.2 The «before html» insertion mode
      3. 13.2.6.4.3 The «before head» insertion mode
      4. 13.2.6.4.4 The «in head» insertion mode
      5. 13.2.6.4.5 The «in head noscript» insertion mode
      6. 13.2.6.4.6 The «after head» insertion mode
      7. 13.2.6.4.7 The «in body» insertion mode
      8. 13.2.6.4.8 The «text» insertion mode
      9. 13.2.6.4.9 The «in table» insertion mode
      10. 13.2.6.4.10 The «in table text» insertion mode
      11. 13.2.6.4.11 The «in caption» insertion mode
      12. 13.2.6.4.12 The «in column group» insertion mode
      13. 13.2.6.4.13 The «in table body» insertion mode
      14. 13.2.6.4.14 The «in row» insertion mode
      15. 13.2.6.4.15 The «in cell» insertion mode
      16. 13.2.6.4.16 The «in select» insertion mode
      17. 13.2.6.4.17 The «in select in table» insertion mode
      18. 13.2.6.4.18 The «in template» insertion mode
      19. 13.2.6.4.19 The «after body» insertion mode
      20. 13.2.6.4.20 The «in frameset» insertion mode
      21. 13.2.6.4.21 The «after frameset» insertion mode
      22. 13.2.6.4.22 The «after after body» insertion mode
      23. 13.2.6.4.23 The «after after frameset» insertion mode
    5. 13.2.6.5 The rules for parsing tokens in foreign content
  7. 13.2.7 The end
  8. 13.2.8 Speculative HTML parsing
  9. 13.2.9 Coercing an HTML DOM into an infoset
  10. 13.2.10 An introduction to error handling and strange cases in the parser
    1. 13.2.10.1 Misnested tags: <b><i></b></i>
    2. 13.2.10.2 Misnested tags: <b><p></b></p>
    3. 13.2.10.3 Unexpected markup in tables
    4. 13.2.10.4 Scripts that modify the page as it is being parsed
    5. 13.2.10.5 The execution of scripts that are moving across multiple documents
    6. 13.2.10.6 Unclosed formatting elements
2. 13.3 Serializing HTML fragments
3. 13.4 Parsing HTML fragments

13.2 Parsing HTML documents

This section only applies to user agents, data mining tools, and conformance
checkers.

The rules for parsing XML documents into DOM trees are covered by the next
section, entitled «The XML syntax».

User agents must use the parsing rules described in this section to generate the DOM trees from
text/html resources. Together, these rules define what is referred to as the
HTML parser.

While the HTML syntax described in this specification bears a close resemblance to SGML and
XML, it is a separate language with its own parsing rules.

Some earlier versions of HTML (in particular from HTML2 to HTML4) were based on SGML and used
SGML parsing rules. However, few (if any) web browsers ever implemented true SGML parsing for
HTML documents; the only user agents to strictly handle HTML as an SGML application have
historically been validators. The resulting confusion — with validators claiming documents
to have one representation while widely deployed web browsers interoperably implemented a
different representation — has wasted decades of productivity. This version of HTML thus
returns to a non-SGML basis.

Authors interested in using SGML tools in their authoring pipeline are encouraged to use XML
tools and the XML serialization of HTML.

For the purposes of conformance checkers, if a resource is determined to be in the HTML
syntax, then it is an HTML document.

As stated in the terminology section,
references to element types that do not explicitly specify a
namespace always refer to elements in the HTML namespace. For example, if the spec
talks about «a element», then that is an element with the local name «menu«, the namespace «http://www.w3.org/1999/xhtml«, and
the interface . Where possible, references to such elements are
hyperlinked to their definition.

13.2.1 Overview of the parsing model

The input to the HTML parsing process consists of a stream of code
points, which is passed through a tokenization stage followed by a tree
construction stage. The output is a Document object.

Implementations that do not support scripting do not
have to actually create a DOM Document object, but the DOM tree in such cases is
still used as the model for the rest of the specification.

In the common case, the data handled by the tokenization stage comes from the network, but
it can also come from script running in the user
agent, e.g. using the document.write() API.

There is only one set of states for the tokenizer stage and the tree
construction stage, but the tree construction stage is reentrant, meaning that while the tree
construction stage is handling one token, the tokenizer might be resumed, causing further tokens
to be emitted and processed before the first token’s processing is complete.

In the following example, the tree construction stage will be called upon to handle a «p»
start tag token while handling the «script» end tag token:

...
<script>
 document.write('<p>');
</script>
...

To handle these cases, parsers have a script nesting level, which must be initially
set to zero, and a parser pause flag, which must be initially set to false.

13.2.2 Parse errors

This specification defines the parsing rules for HTML documents, whether they are syntactically
correct or not. Certain points in the parsing algorithm are said to be parse errors. The error handling for parse errors is well-defined (that’s the
processing rules described throughout this specification), but user agents, while parsing an HTML
document, may abort the parser at the first parse
error that they encounter for which they do not wish to apply the rules described in this
specification.

Conformance checkers must report at least one parse error condition to the user if one or more
parse error conditions exist in the document and must not report parse error conditions if none
exist in the document. Conformance checkers may report more than one parse error condition if more
than one parse error condition exists in the document.

Parse errors are only errors with the syntax of HTML. In addition to
checking for parse errors, conformance checkers will also verify that the document obeys all the
other conformance requirements described in this specification.

Some parse errors have dedicated codes outlined in the table below that should be used by
conformance checkers in reports.

Error descriptions in the table below are non-normative.

Code	Description
abrupt-closing-of-empty-comment	This error occurs if the parser encounters an empty comment that is abruptly closed by a U+003E (>) code point (i.e., `<!-->` or `<!--->`). The parser behaves as if the comment is closed correctly.
abrupt-doctype-public-identifier	This error occurs if the parser encounters a U+003E (>) code point in the DOCTYPE public identifier (e.g., `<!DOCTYPE html PUBLIC "foo>`). In such a case, if the DOCTYPE is correctly placed as a document preamble, the parser sets the `Document` to quirks mode.
abrupt-doctype-system-identifier	This error occurs if the parser encounters a U+003E (>) code point in the DOCTYPE system identifier (e.g., `<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "foo>`). In such a case, if the DOCTYPE is correctly placed as a document preamble, the parser sets the `Document` to quirks mode.
absence-of-digits-in-numeric-character-reference	This error occurs if the parser encounters a numeric character reference that doesn’t contain any digits (e.g., `&#qux;`). In this case the parser doesn’t resolve the character reference.
cdata-in-html-content	This error occurs if the parser encounters a CDATA section outside of foreign content (SVG or MathML). The parser treats such CDATA sections (including leading «`[CDATA[`» and trailing «`]]`» strings) as comments.
character-reference-outside-unicode-range	This error occurs if the parser encounters a numeric character reference that references a code point that is greater than the valid Unicode range. The parser resolves such a character reference to a U+FFFD REPLACEMENT CHARACTER.
control-character-in-input-stream	This error occurs if the input stream contains a control code point that is not ASCII whitespace or U+0000 NULL. Such code points are parsed as-is and usually, where parsing rules don’t apply any additional restrictions, make their way into the DOM.
control-character-reference	This error occurs if the parser encounters a numeric character reference that references a control code point that is not ASCII whitespace or is a U+000D CARRIAGE RETURN. The parser resolves such character references as-is except C1 control references that are replaced according to the numeric character reference end state.
end-tag-with-attributes	This error occurs if the parser encounters an end tag with attributes. Attributes in end tags are ignored and do not make their way into the DOM.
duplicate-attribute	This error occurs if the parser encounters an attribute in a tag that already has an attribute with the same name. The parser ignores all such duplicate occurrences of the attribute.
end-tag-with-trailing-solidus	This error occurs if the parser encounters an end tag that has a U+002F (/) code point right before the closing U+003E (>) code point (e.g., `</div/>`). Such a tag is treated as a regular end tag.
eof-before-tag-name	This error occurs if the parser encounters the end of the input stream where a tag name is expected. In this case the parser treats the beginning of a start tag (i.e., `<`) or an end tag (i.e., `</`) as text content.
eof-in-cdata	This error occurs if the parser encounters the end of the input stream in a CDATA section. The parser treats such CDATA sections as if they are closed immediately before the end of the input stream.
eof-in-comment	This error occurs if the parser encounters the end of the input stream in a comment. The parser treats such comments as if they are closed immediately before the end of the input stream.
eof-in-doctype	This error occurs if the parser encounters the end of the input stream in a DOCTYPE. In such a case, if the DOCTYPE is correctly placed as a document preamble, the parser sets the `Document` to quirks mode.
eof-in-script-html-comment-like-text	This error occurs if the parser encounters the end of the input stream in text that resembles an HTML comment inside `script` element content (e.g., `<script><!-- foo`). Syntactic structures that resemble HTML comments in `script` elements are parsed as text content. They can be a part of a scripting language-specific syntactic structure or be treated as an HTML-like comment, if the scripting language supports them (e.g., parsing rules for HTML-like comments can be found in Annex B of the JavaScript specification). The common reason for this error is a violation of the restrictions for contents of `script` elements. [JAVASCRIPT]
eof-in-tag	This error occurs if the parser encounters the end of the input stream in a start tag or an end tag (e.g., `<div id=`). Such a tag is ignored.
incorrectly-closed-comment	This error occurs if the parser encounters a comment that is closed by the «`--!>`» code point sequence. The parser treats such comments as if they are correctly closed by the «`-->`» code point sequence.
incorrectly-opened-comment	This error occurs if the parser encounters the «`<!`» code point sequence that is not immediately followed by two U+002D (-) code points and that is not the start of a DOCTYPE or a CDATA section. All content that follows the «`<!`» code point sequence up to a U+003E (>) code point (if present) or to the end of the input stream is treated as a comment. One possible cause of this error is using an XML markup declaration (e.g., `<!ELEMENT br EMPTY>`) in HTML.
invalid-character-sequence-after-doctype-name	This error occurs if the parser encounters any code point sequence other than «`PUBLIC`» and «`SYSTEM`» keywords after a DOCTYPE name. In such a case, the parser ignores any following public or system identifiers, and if the DOCTYPE is correctly placed as a document preamble, and if the parser cannot change the mode flag is false, sets the `Document` to quirks mode.
invalid-first-character-of-tag-name	This error occurs if the parser encounters a code point that is not an ASCII alpha where first code point of a start tag name or an end tag name is expected. If a start tag was expected such code point and a preceding U+003C (<) is treated as text content, and all content that follows is treated as markup. Whereas, if an end tag was expected, such code point and all content that follows up to a U+003E (>) code point (if present) or to the end of the input stream is treated as a comment. For example, consider the following markup: `<42></42>` This will be parsed into: `html` `head` `body` `#text`: <42> : 42 While the first code point of a tag name is limited to an ASCII alpha, a wide range of code points (including ASCII digits) is allowed in subsequent positions.
missing-attribute-value	This error occurs if the parser encounters a U+003E (>) code point where an attribute value is expected (e.g., `<div id=>`). The parser treats the attribute as having an empty value.
missing-doctype-name	This error occurs if the parser encounters a DOCTYPE that is missing a name (e.g., `<!DOCTYPE>`). In such a case, if the DOCTYPE is correctly placed as a document preamble, the parser sets the `Document` to quirks mode.
missing-doctype-public-identifier	This error occurs if the parser encounters a U+003E (>) code point where start of the DOCTYPE public identifier is expected (e.g., `<!DOCTYPE html PUBLIC >`). In such a case, if the DOCTYPE is correctly placed as a document preamble, the parser sets the `Document` to quirks mode.
missing-doctype-system-identifier	This error occurs if the parser encounters a U+003E (>) code point where start of the DOCTYPE system identifier is expected (e.g., `<!DOCTYPE html SYSTEM >`). In such a case, if the DOCTYPE is correctly placed as a document preamble, the parser sets the `Document` to quirks mode.
missing-end-tag-name	This error occurs if the parser encounters a U+003E (>) code point where an end tag name is expected, i.e., `</>`. The parser ignores the whole «`</>`» code point sequence.
missing-quote-before-doctype-public-identifier	This error occurs if the parser encounters the DOCTYPE public identifier that is not preceded by a quote (e.g., `<!DOCTYPE html PUBLIC -//W3C//DTD HTML 4.01//EN">`). In such a case, the parser ignores the public identifier, and if the DOCTYPE is correctly placed as a document preamble, sets the `Document` to quirks mode.
missing-quote-before-doctype-system-identifier	This error occurs if the parser encounters the DOCTYPE system identifier that is not preceded by a quote (e.g., `<!DOCTYPE html SYSTEM http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">`). In such a case, the parser ignores the system identifier, and if the DOCTYPE is correctly placed as a document preamble, sets the `Document` to quirks mode.
missing-semicolon-after-character-reference	This error occurs if the parser encounters a character reference that is not terminated by a U+003B (;) code point. Usually the parser behaves as if character reference is terminated by the U+003B (;) code point; however, there are some ambiguous cases in which the parser includes subsequent code points in the character reference. For example, `¬in` will be parsed as «`¬in`» whereas `&notin` will be parsed as «`∉`«.
missing-whitespace-after-doctype-public-keyword	This error occurs if the parser encounters a DOCTYPE whose «`PUBLIC`» keyword and public identifier are not separated by ASCII whitespace. In this case the parser behaves as if ASCII whitespace is present.
missing-whitespace-after-doctype-system-keyword	This error occurs if the parser encounters a DOCTYPE whose «`SYSTEM`» keyword and system identifier are not separated by ASCII whitespace. In this case the parser behaves as if ASCII whitespace is present.
missing-whitespace-before-doctype-name	This error occurs if the parser encounters a DOCTYPE whose «`DOCTYPE`» keyword and name are not separated by ASCII whitespace. In this case the parser behaves as if ASCII whitespace is present.
missing-whitespace-between-attributes	This error occurs if the parser encounters attributes that are not separated by ASCII whitespace (e.g., `<div id="foo"class="bar">`). In this case the parser behaves as if ASCII whitespace is present.
missing-whitespace-between-doctype-public-and-system-identifiers	This error occurs if the parser encounters a DOCTYPE whose public and system identifiers are not separated by ASCII whitespace. In this case the parser behaves as if ASCII whitespace is present.
nested-comment	This error occurs if the parser encounters a nested comment (e.g., `<!-- <!-- nested --> -->`). Such a comment will be closed by the first occurring «`-->`» code point sequence and everything that follows will be treated as markup.
noncharacter-character-reference	This error occurs if the parser encounters a numeric character reference that references a noncharacter. The parser resolves such character references as-is.
noncharacter-in-input-stream	This error occurs if the input stream contains a noncharacter. Such code points are parsed as-is and usually, where parsing rules don’t apply any additional restrictions, make their way into the DOM.
non-void-html-element-start-tag-with-trailing-solidus	This error occurs if the parser encounters a start tag for an element that is not in the list of void elements or is not a part of foreign content (i.e., not an SVG or MathML element) that has a U+002F (/) code point right before the closing U+003E (>) code point. The parser behaves as if the U+002F (/) is not present. For example, consider the following markup: `<div/><span></span><span></span>` This will be parsed into: `html` `head` `body` `div` `span` `span` The trailing U+002F (/) in a start tag name can be used only in foreign content to specify self-closing tags. (Self-closing tags don’t exist in HTML.) It is also allowed for void elements, but doesn’t have any effect in this case.
null-character-reference	This error occurs if the parser encounters a numeric character reference that references a U+0000 NULL code point. The parser resolves such character references to a U+FFFD REPLACEMENT CHARACTER.
surrogate-character-reference	This error occurs if the parser encounters a numeric character reference that references a surrogate. The parser resolves such character references to a U+FFFD REPLACEMENT CHARACTER.
surrogate-in-input-stream	This error occurs if the input stream contains a surrogate. Such code points are parsed as-is and usually, where parsing rules don’t apply any additional restrictions, make their way into the DOM. Surrogates can only find their way into the input stream via script APIs such as `document.write()`.
unexpected-character-after-doctype-system-identifier	This error occurs if the parser encounters any code points other than ASCII whitespace or closing U+003E (>) after the DOCTYPE system identifier. The parser ignores these code points.
unexpected-character-in-attribute-name	This error occurs if the parser encounters a U+0022 («), U+0027 (‘), or U+003C (<) code point in an attribute name. The parser includes such code points in the attribute name. Code points that trigger this error are usually a part of another syntactic construct and can be a sign of a typo around the attribute name. For example, consider the following markup: `<div foo<div>` Due to a forgotten U+003E (>) code point after `foo` the parser treats this markup as a single `div` element with a «`foo<div`» attribute. As another example of this error, consider the following markup: `<div id'bar'>` Due to a forgotten U+003D (=) code point between an attribute name and value the parser treats this markup as a `div` element with the attribute «`id'bar'`» that has an empty value.
unexpected-character-in-unquoted-attribute-value	This error occurs if the parser encounters a U+0022 («), U+0027 (‘), U+003C (<), U+003D (=), or U+0060 (`) code point in an unquoted attribute value. The parser includes such code points in the attribute value. Code points that trigger this error are usually a part of another syntactic construct and can be a sign of a typo around the attribute value. U+0060 (`) is in the list of code points that trigger this error because certain legacy user agents treat it as a quote. For example, consider the following markup: `<div foo=b'ar'>` Due to a misplaced U+0027 (‘) code point the parser sets the value of the «`foo`» attribute to «`b'ar'`«.
unexpected-equals-sign-before-attribute-name	This error occurs if the parser encounters a U+003D (=) code point before an attribute name. In this case the parser treats U+003D (=) as the first code point of the attribute name. The common reason for this error is a forgotten attribute name. For example, consider the following markup: `<div foo="bar" ="baz">` Due to a forgotten attribute name the parser treats this markup as a `div` element with two attributes: a «`foo`» attribute with a «`bar`» value and a «`="baz"`» attribute with an empty value.
unexpected-null-character	This error occurs if the parser encounters a U+0000 NULL code point in the input stream in certain positions. In general, such code points are either ignored or, for security reasons, replaced with a U+FFFD REPLACEMENT CHARACTER.
unexpected-question-mark-instead-of-tag-name	This error occurs if the parser encounters a U+003F (?) code point where first code point of a start tag name is expected. The U+003F (?) and all content that follows up to a U+003E (>) code point (if present) or to the end of the input stream is treated as a comment. For example, consider the following markup: `<?xml-stylesheet type="text/css" href="style.css"?>` This will be parsed into: : ?xml-stylesheet type=»text/css» href=»style.css»? `html` `head` `body` The common reason for this error is an XML processing instruction (e.g., `<?xml-stylesheet type="text/css" href="style.css"?>`) or an XML declaration (e.g., `<?xml version="1.0" encoding="UTF-8"?>`) being used in HTML.
unexpected-solidus-in-tag	This error occurs if the parser encounters a U+002F (/) code point that is not a part of a quoted attribute value and not immediately followed by a U+003E (>) code point in a tag (e.g., `<div / id="foo">`). In this case the parser behaves as if it encountered ASCII whitespace.
unknown-named-character-reference	This error occurs if the parser encounters an ambiguous ampersand. In this case the parser doesn’t resolve the character reference.

13.2.3 The input byte stream

The stream of code points that comprises the input to the tokenization stage will be initially
seen by the user agent as a stream of bytes (typically coming over the network or from the local
file system). The bytes encode the actual characters according to a particular character
encoding, which the user agent uses to decode the bytes into characters.

For XML documents, the algorithm user agents are required to use to determine the
character encoding is given by XML. This section does not apply to XML
documents. [XML]

Usually, the encoding sniffing algorithm defined below is used to determine the
character encoding.

Given a character encoding, the bytes in the input byte stream must be converted
to characters for the tokenizer’s input stream, by passing the input byte
stream and character encoding to decode.

A leading Byte Order Mark (BOM) causes the character encoding argument to be
ignored and will itself be skipped.

Bytes or sequences of bytes in the original byte stream that did not conform to
the Encoding standard (e.g. invalid UTF-8 byte sequences in a UTF-8 input byte stream) are errors
that conformance checkers are expected to report. [ENCODING]

The decoder algorithms describe how to handle invalid input; for security
reasons, it is imperative that those rules be followed precisely. Differences in how invalid byte
sequences are handled can result in, amongst other problems, script injection vulnerabilities
(«XSS»).

When the HTML parser is decoding an input byte stream, it uses a character encoding and a confidence. The confidence is either tentative,
certain, or irrelevant. The encoding used, and whether the confidence in that
encoding is tentative or certain, is used
during the parsing to determine whether to change the encoding. If no encoding is
necessary, e.g. because the parser is operating on a Unicode stream and doesn’t have to use a
character encoding at all, then the confidence is
irrelevant.

Some algorithms feed the parser by directly adding characters to the input
stream rather than adding bytes to the input byte stream.

13.2.3.1 Parsing with a known character encoding

When the HTML parser is to operate on an input byte stream that has a known
definite encoding, then the character encoding is that encoding and the confidence is certain.

13.2.3.2 Determining the character encoding

In some cases, it might be impractical to unambiguously determine the encoding before parsing
the document. Because of this, this specification provides for a two-pass mechanism with an
optional pre-scan. Implementations are allowed, as described below, to apply a simplified parsing
algorithm to whatever bytes they have available before beginning to parse the document. Then, the
real parser is started, using a tentative encoding derived from this pre-parse and other
out-of-band metadata. If, while the document is being loaded, the user agent discovers a character
encoding declaration that conflicts with this information, then the parser can get reinvoked to
perform a parse of the document with the real encoding.

User agents must use the following algorithm, called the encoding
sniffing algorithm, to determine the character encoding to use when decoding a document in
the first pass. This algorithm takes as input any out-of-band metadata available to the user agent
(e.g. the Content-Type metadata of the document) and all the
bytes available so far, and returns a character encoding and a confidence that is either tentative or
certain.

If the result of BOM sniffing is an encoding, return that
encoding with confidence certain.

Although the decode algorithm will itself change the encoding to
use based on the presence of a byte order mark, this algorithm sniffs the BOM as well in order
to set the correct document’s character encoding and confidence.
If the user has explicitly instructed the user agent to override the document’s character
encoding with a specific encoding, optionally return that encoding with the confidence certain.

Typically, user agents remember such user requests across sessions, and in some
cases apply them to documents in iframes as well.
The user agent may wait for more bytes of the resource to be available, either in this step
or at any later step in this algorithm. For instance, a user agent might wait 500ms or 1024
bytes, whichever came first. In general preparsing the source to find the encoding improves
performance, as it reduces the need to throw away the data structures used when parsing upon
finding the encoding information. However, if the user agent delays too long to obtain data to
determine the encoding, then the cost of the delay could outweigh any performance improvements
from the preparse.

The authoring conformance requirements for character encoding declarations limit
them to only appearing in the first 1024 bytes. User agents are
therefore encouraged to use the prescan algorithm below (as invoked by these steps) on the first
1024 bytes, but not to stall beyond that.
If the transport layer specifies a character encoding, and it is supported, return that
encoding with the confidence certain.
Optionally prescan the byte
stream to determine its encoding, with the end
condition being when the user agent decides that scanning further bytes would not be
efficient. User agents are encouraged to only prescan the first 1024 bytes. User agents may
decide that scanning any bytes is not efficient, in which case these substeps are
entirely skipped.

The aforementioned algorithm returns either a character encoding or failure. If it returns a
character encoding, then return the same encoding, with confidence tentative.
If the HTML parser for which this algorithm is being run is associated with a
Document d whose container
document is non-null, then:
1. Let parentDocument be d‘s container document.
2. If parentDocument‘s origin is
  same origin with d‘s origin and parentDocument‘s character encoding is not
  UTF-16BE/LE, then return parentDocument‘s character encoding, with the confidence tentative.
Otherwise, if the user agent has information on the likely encoding for this page, e.g.
based on the encoding of the page when it was last visited, then return that encoding, with the
confidence tentative.
The user agent may attempt to autodetect the character encoding from applying frequency
analysis or other algorithms to the data stream. Such algorithms may use information about the
resource other than the resource’s contents, including the address of the resource. If
autodetection succeeds in determining a character encoding, and that encoding is a supported
encoding, then return that encoding, with the confidence tentative.
[UNIVCHARDET]

User agents are generally discouraged from attempting to autodetect encodings
for resources obtained over the network, since doing so involves inherently non-interoperable
heuristics. Attempting to detect encodings based on an HTML document’s preamble is especially
tricky since HTML markup typically uses only ASCII characters, and HTML documents tend to begin
with a lot of markup rather than with text content.

The UTF-8 encoding has a highly detectable bit pattern. Files from the local
file system that contain bytes with values greater than 0x7F which match the UTF-8 pattern are
very likely to be UTF-8, while documents with byte sequences that do not match it are very
likely not. When a user agent can examine the whole file, rather than just the preamble,
detecting for UTF-8 specifically can be especially effective. [PPUTF8] [UTF8DET]

Otherwise, return an implementation-defined or user-specified default character
encoding, with the confidence
tentative.

In controlled environments or in environments where the encoding of documents can be
prescribed (for example, for user agents intended for dedicated use in new networks), the
comprehensive UTF-8 encoding is suggested.

In other environments, the default encoding is typically dependent on the user’s locale (an
approximation of the languages, and thus often encodings, of the pages that the user is likely
to frequent). The following table gives suggested defaults based on the user’s locale, for
compatibility with legacy content. Locales are identified by BCP 47 language tags. [BCP47] [ENCODING]

Locale language	Suggested default encoding
ar	Arabic	windows-1256
az	Azeri	windows-1254
ba	Bashkir	windows-1251
be	Belarusian	windows-1251
bg	Bulgarian	windows-1251
cs	Czech	windows-1250
el	Greek	ISO-8859-7
et	Estonian	windows-1257
fa	Persian	windows-1256
he	Hebrew	windows-1255
hr	Croatian	windows-1250
hu	Hungarian	ISO-8859-2
ja	Japanese	Shift_JIS
kk	Kazakh	windows-1251
ko	Korean	EUC-KR
ku	Kurdish	windows-1254
ky	Kyrgyz	windows-1251
lt	Lithuanian	windows-1257
lv	Latvian	windows-1257
mk	Macedonian	windows-1251
pl	Polish	ISO-8859-2
ru	Russian	windows-1251
sah	Yakut	windows-1251
sk	Slovak	windows-1250
sl	Slovenian	ISO-8859-2
sr	Serbian	windows-1251
tg	Tajik	windows-1251
th	Thai	windows-874
tr	Turkish	windows-1254
tt	Tatar	windows-1251
uk	Ukrainian	windows-1251
vi	Vietnamese	windows-1258
zh-Hans, zh-CN, zh-SG	Chinese, Simplified	GBK
zh-Hant, zh-HK, zh-MO, zh-TW	Chinese, Traditional	Big5
All other locales	windows-1252

The contents of this table are derived from the intersection of
Windows, Chrome, and Firefox defaults.

The document’s character encoding must immediately be set to the value returned
from this algorithm, at the same time as the user agent uses the returned value to select the
decoder to use for the input byte stream.

When an algorithm requires a user agent to prescan a byte stream to determine its
encoding, given some defined end condition, then it must run the following
steps. If at any point during these steps (including during instances of the get an attribute algorithm invoked by this
one) the user agent either runs out of bytes (meaning the position pointer created in
the first step below goes beyond the end of the byte stream obtained so far) or reaches its
end condition, then abort the prescan a byte stream to determine its
encoding algorithm and return the result get an XML encoding applied to the same
bytes that the prescan a byte stream to determine its encoding algorithm was applied
to. Otherwise, these steps will return a character encoding.

Let fallback encoding be null.
Let position be a pointer to a byte in the input byte stream, initially
pointing at the first byte.
Prescan for UTF-16 XML declarations: If position points to:

A sequence of bytes starting with: 0x3C, 0x0, 0x3F, 0x0, 0x78, 0x0 (case-sensitive UTF-16
little-endian ‘<?x’)

Return UTF-16LE.

A sequence of bytes starting with: 0x0, 0x3C, 0x0, 0x3F, 0x0, 0x78 (case-sensitive UTF-16
big-endian ‘<?x’)

Return UTF-16BE.

For historical reasons, the prefix is two bytes longer than in Appendix F of XML and the
encoding name is not checked.
Loop: If position points to:
A sequence of bytes starting with: 0x3C 0x21 0x2D 0x2D (`<!--`)

Advance the position pointer so that it points at the first 0x3E byte
which is preceded by two 0x2D bytes (i.e. at the end of an ASCII ‘—>’ sequence) and comes
after the 0x3C byte that was found. (The two 0x2D bytes can be the same as those in the
‘<!—‘ sequence.)

A sequence of bytes starting with: 0x3C, 0x4D or 0x6D, 0x45 or 0x65, 0x54 or 0x74, 0x41 or 0x61, and one of 0x09, 0x0A, 0x0C, 0x0D, 0x20, 0x2F (case-insensitive ASCII ‘<meta’ followed by a space or slash)
1. Advance the position pointer so that it points at the next 0x09,
  0x0A, 0x0C, 0x0D, 0x20, or 0x2F byte (the one in sequence of characters matched
  above).
2. Let attribute list be an empty list of strings.
3. Let got pragma be false.
4. Let need pragma be null.
5. Let charset be the null value (which, for the purposes of this
  algorithm, is distinct from an unrecognized encoding or the empty string).
6. Attributes: Get an
  attribute and its value. If no attribute was sniffed, then jump to the
  processing step below.
7. If the attribute’s name is already in attribute list, then return
  to the step labeled attributes.
8. Add the attribute’s name to attribute list.
9. Run the appropriate step from the following list, if one applies:
  
  If the attribute’s name is «http-equiv«
  
  If the attribute’s value is «content-type«, then set got pragma to true.
  
  If the attribute’s name is «content«
  
  Apply the algorithm for extracting a character encoding from a
  meta element, giving the attribute’s value as the string to parse. If a
  character encoding is returned, and if charset is still set to null,
  let charset be the encoding returned, and set need pragma to true.
  
  If the attribute’s name is «charset«
  
  Let charset be the result of getting an encoding
  from the attribute’s value, and set need pragma to false.
10. Return to the step labeled attributes.
11. Processing: If need pragma is null, then jump to the step
  below labeled next byte.
12. If need pragma is true but got pragma is
  false, then jump to the step below labeled next byte.
13. If charset is failure, then jump to the step below labeled next
  byte.
14. If charset is UTF-16BE/LE, then set charset to
  UTF-8.
15. If charset is x-user-defined, then set charset to
  windows-1252.
16. Return charset.
A sequence of bytes starting with a 0x3C byte (<), optionally a 0x2F byte (/), and
finally a byte in the range 0x41-0x5A or 0x61-0x7A (A-Z or a-z)
1. Advance the position pointer so that it points at the next 0x09 (HT),
  0x0A (LF), 0x0C (FF), 0x0D (CR), 0x20 (SP), or 0x3E (>) byte.
2. Repeatedly get an attribute
  until no further attributes can be found, then jump to the step below labeled next
  byte.
A sequence of bytes starting with: 0x3C 0x21 (`<!`)

A sequence of bytes starting with: 0x3C 0x2F (`</`)

A sequence of bytes starting with: 0x3C 0x3F (`<?`)

Advance the position pointer so that it points at the first 0x3E byte (>) that
comes after the 0x3C byte that was found.

Any other byte

Do nothing with that byte.
Next byte: Move position so it points at the next byte in the
input byte stream, and return to the step above labeled loop.

When the prescan a byte stream to determine its encoding algorithm says to get an attribute, it means doing this:

If the byte at position is one of 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR),
0x20 (SP), or 0x2F (/) then advance position to the next byte and redo this
step.
If the byte at position is 0x3E (>), then abort the get an attribute algorithm. There isn’t
one.
Otherwise, the byte at position is the start of the attribute name.
Let attribute name and attribute value be the empty
string.
Process the byte at position as follows:

If it is 0x3D (=), and the attribute name is longer than the empty string

Advance position to the next byte and jump to the step below labeled
value.

If it is 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), or 0x20 (SP)

Jump to the step below labeled spaces.

If it is 0x2F (/) or 0x3E (>)

Abort the get an attribute
algorithm. The attribute’s name is the value of attribute name, its value
is the empty string.

If it is in the range 0x41 (A) to 0x5A (Z)

Append the code point b+0x20 to attribute name
(where b is the value of the byte at position). (This converts the input
to lowercase.)

Anything else

Append the code point with the same value as the byte at position to
attribute name. (It doesn’t actually matter how bytes outside the ASCII range are
handled here, since only ASCII bytes can contribute to the detection of a character
encoding.)
Advance position to the next byte and return to the previous
step.
Spaces: If the byte at position is one of 0x09 (HT), 0x0A (LF), 0x0C
(FF), 0x0D (CR), or 0x20 (SP) then advance position to the next byte, then, repeat
this step.
If the byte at position is not 0x3D (=), abort the get an attribute algorithm. The attribute’s
name is the value of attribute name, its value is the empty string.
Advance position past the 0x3D (=) byte.
Value: If the byte at position is one of 0x09 (HT), 0x0A (LF), 0x0C
(FF), 0x0D (CR), or 0x20 (SP) then advance position to the next byte, then, repeat
this step.
Process the byte at position as follows:
If it is 0x22 («) or 0x27 (‘)
1. Let b be the value of the byte at position.
2. Quote loop: Advance position to the next byte.
3. If the value of the byte at position is the value of b, then advance position to the next byte and abort the
  «get an attribute» algorithm. The attribute’s name is the value of attribute name, and its value is the value of attribute value.
4. Otherwise, if the value of the byte at position is in the range 0x41 (A) to
  0x5A (Z), then append a code point to attribute value whose value is 0x20 more
  than the value of the byte at position.
5. Otherwise, append a code point to attribute value whose value is the same as
  the value of the byte at position.
6. Return to the step above labeled quote loop.
If it is 0x3E (>)

Abort the get an attribute
algorithm. The attribute’s name is the value of attribute name, its value
is the empty string.

If it is in the range 0x41 (A) to 0x5A (Z)

Append a code point b+0x20 to attribute value
(where b is the value of the byte at position). Advance
position to the next byte.

Anything else

Append a code point with the same value as the byte at position to
attribute value. Advance position to the next byte.
Process the byte at position as
follows:

If it is 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), 0x20 (SP), or 0x3E (>)

Abort the get an attribute
algorithm. The attribute’s name is the value of attribute name and its
value is the value of attribute value.

If it is in the range 0x41 (A) to 0x5A (Z)

Append a code point b+0x20 to attribute value
(where b is the value of the byte at position).

Anything else

Append a code point with the same value as the byte at position to
attribute value.
Advance position to the next byte and return to the previous
step.

When the prescan a byte stream to determine its encoding algorithm is aborted
without returning an encoding, get an XML
encoding means doing this.

Looking for syntax resembling an XML declaration, even in text/html,
is necessary for compatibility with existing content.

Let encodingPosition be a pointer to the start of the stream.
If encodingPosition does not point to the start of a byte sequence 0x3C, 0x3F,
0x78, 0x6D, 0x6C (`<?xml`), then return failure.
Let xmlDeclarationEnd be a pointer to the next byte in the input byte stream
which is 0x3E (>). If there is no such byte, then return failure.
Set encodingPosition to the position of the first occurrence of the subsequence
of bytes 0x65, 0x6E, 0x63, 0x6F, 0x64, 0x69, 0x6E, 0x67 (`encoding`) at or
after the current encodingPosition. If there is no such sequence, then return
failure.
Advance encodingPosition past the 0x67 (g) byte.
While the byte at encodingPosition is less than or equal to 0x20 (i.e., it is
either an ASCII space or control character), advance encodingPosition to the next
byte.
If the byte at encodingPosition is not 0x3D (=), then return failure.
Advance encodingPosition to the next byte.
While the byte at encodingPosition is less than or equal to 0x20 (i.e., it is
either an ASCII space or control character), advance encodingPosition to the next
byte.
Let quoteMark be the byte at encodingPosition.
If quoteMark is not either 0x22 («) or 0x27 (‘), then return failure.
Advance encodingPosition to the next byte.
Let encodingEndPosition be the position of the next occurrence of
quoteMark at or after encodingPosition. If quoteMark does not
occur again, then return failure.
Let potentialEncoding be the sequence of the bytes between
encodingPosition (inclusive) and encodingEndPosition (exclusive).
If potentialEncoding contains one or more bytes whose byte value is 0x20 or
below, then return failure.
Let encoding be the result of getting an encoding given
potentialEncoding isomorphic decoded.
If the encoding is UTF-16BE/LE, then change it to
UTF-8.
Return encoding.

For the sake of interoperability, user agents should not use a pre-scan algorithm that returns
different results than the one described above. (But, if you do, please at least let us know, so
that we can improve this algorithm and benefit everyone…)

13.2.3.3 Character encodings

User agents must support the encodings defined in Encoding, including, but
not limited to,
UTF-8,
ISO-8859-2,
ISO-8859-7,
ISO-8859-8,
windows-874,
windows-1250,
windows-1251,
windows-1252,
windows-1254,
windows-1255,
windows-1256,
windows-1257,
windows-1258,
GBK,
Big5,
ISO-2022-JP,
Shift_JIS,
EUC-KR,
UTF-16BE,
UTF-16LE,
UTF-16BE/LE, and
x-user-defined.
User agents must not support other encodings.

The above prohibits supporting, for example, CESU-8, UTF-7, BOCU-1, SCSU, EBCDIC,
and UTF-32. This specification does not make any attempt to support prohibited encodings in its
algorithms; support and use of prohibited encodings would thus lead to unexpected behavior. [CESU8] [UTF7] [BOCU1] [SCSU]

13.2.3.4 Changing the encoding while parsing

When the parser requires the user agent to change the encoding, it must run the
following steps. This might happen if the encoding sniffing algorithm described above
failed to find a character encoding, or if it found a character encoding that was not the actual
encoding of the file.

If the encoding that is already being used to interpret the input stream is
UTF-16BE/LE, then set the confidence to certain and return. The new
encoding is ignored; if it was anything but the same encoding, then it would be clearly
incorrect.
If the new encoding is UTF-16BE/LE, then change it to
UTF-8.
If the new encoding is x-user-defined, then change it to
windows-1252.
If the new encoding is identical or equivalent to the encoding that is already being used
to interpret the input stream, then set the confidence to certain and return.
This happens when the encoding information found in the file matches what the encoding
sniffing algorithm determined to be the encoding, and in the second pass through the
parser if the first pass found that the encoding sniffing algorithm described in the earlier
section failed to find the right encoding.
If all the bytes up to the last byte converted by the current decoder have the same
Unicode interpretations in both the current encoding and the new encoding, and if the user agent
supports changing the converter on the fly, then the user agent may change to the new converter
for the encoding on the fly. Set the document’s character encoding and the encoding
used to convert the input stream to the new encoding, set the confidence to certain, and return.
Otherwise, restart the navigate algorithm, with historyHandling set to «replace» and
other inputs kept the same, but this time skip the encoding sniffing algorithm and
instead just set the encoding to the new encoding and the confidence to certain. Whenever possible,
this should be done without actually contacting the network layer (the bytes should be re-parsed
from memory), even if, e.g., the document is marked as not being cacheable. If this is not
possible and contacting the network layer would involve repeating a request that uses a method
other than `GET`, then instead set the confidence to certain and ignore the new
encoding. The resource will be misinterpreted. User agents may notify the user of the situation,
to aid in application development.

This algorithm is only invoked when a new encoding is found declared on a
meta element.

13.2.3.5 Preprocessing the input stream

The input stream consists of the characters pushed into it as the input byte
stream is decoded or from the various APIs that directly manipulate the input stream.

Any occurrences of surrogates are surrogate-in-input-stream
parse errors. Any occurrences of noncharacters are noncharacter-in-input-stream
parse errors and any occurrences of controls other than ASCII whitespace and U+0000 NULL
characters are control-character-in-input-stream
parse errors.

The handling of U+0000 NULL characters varies based on where the characters are
found and happens at the later stages of the parsing. They are either ignored or, for security
reasons, replaced with a U+FFFD REPLACEMENT CHARACTER. This handling is, by necessity, spread
across both the tokenization stage and the tree construction stage.

Before the tokenization stage, the input stream must be preprocessed by normalizing newlines. Thus, newlines in HTML DOMs are
represented by U+000A LF characters, and there are never any U+000D CR characters in the input to
the tokenization stage.

The next input character is the first character in the input stream
that has not yet been consumed or explicitly ignored by the requirements in
this section. Initially, the next input character is the
first character in the input. The current input character is the last character to have
been consumed.

The insertion point is the position (just before a character or just before the end
of the input stream) where content inserted using document.write() is actually inserted. The insertion point is
relative to the position of the character immediately after it, it is not an absolute offset into
the input stream. Initially, the insertion point is undefined.

The «EOF» character in the tables below is a conceptual character representing the end of the
input stream. If the parser is a script-created parser, then the end of
the input stream is reached when an explicit «EOF» character (inserted by
the document.close() method) is consumed. Otherwise, the
«EOF» character is not a real character in the stream, but rather the lack of any further
characters.

13.2.4 Parse state

13.2.4.1 The insertion mode

The insertion mode is a state variable that controls the primary operation of the
tree construction stage.

Initially, the insertion mode is «initial». It can change to «before
html», «before head», «in head», «in head noscript», «after head»,
«in body», «text», «in table», «in table text», «in caption», «in column
group», «in table body», «in row», «in
cell», «in select», «in select in table», «in template», «after body»,
«in frameset», «after frameset», «after
after body», and «after after
frameset» during the course of the parsing, as described in the tree
construction stage. The insertion mode affects how tokens are processed and whether CDATA
sections are supported.

Several of these modes, namely «in head», «in body», «in
table», and «in select», are special, in
that the other modes defer to them at various times. When the algorithm below says that the user
agent is to do something «using the rules for the m insertion
mode», where m is one of these modes, the user agent must use the rules
described under the m insertion mode’s section, but must leave
the insertion mode unchanged unless the rules in m themselves
switch the insertion mode to a new value.

When the insertion mode is switched to «text» or
«in table text», the original insertion
mode is also set. This is the insertion mode to which the tree construction stage will
return.

Similarly, to parse nested template elements, a stack of template insertion
modes is used. It is initially empty. The current template insertion mode is the
insertion mode that was most recently added to the stack of template insertion modes.
The algorithms in the sections below will push insertion modes onto this stack, meaning
that the specified insertion mode is to be added to the stack, and pop insertion modes from
the stack, which means that the most recently added insertion mode must be removed from the
stack.

When the steps below require the UA to reset the insertion mode appropriately, it
means the UA must follow these steps:

Let last be false.
Let node be the last node in the stack of open
elements.
Loop: If node is the first node in the stack of open elements, then set
last to true, and, if the parser was created as part of the HTML fragment
parsing algorithm (fragment case), set node to the context element passed to that algorithm.
If node is a select element, run these substeps:
1. If last is true, jump to the step below labeled
  done.
2. Let ancestor be node.
3. Loop: If ancestor is the first node in the stack of
  open elements, jump to the step below labeled done.
4. Let ancestor be the node before ancestor in the
  stack of open elements.
5. If ancestor is a template node, jump to the step below
  labeled done.
6. If ancestor is a table node, switch the insertion
  mode to «in select in table»
  and return.
7. Jump back to the step labeled loop.
8. Done: Switch the insertion mode to «in select» and return.
If node is a td or th element and last is
false, then switch the insertion mode to «in
cell» and return.
If node is a tr element, then switch the insertion
mode to «in row» and return.
If node is a tbody, thead, or
tfoot element, then switch the insertion mode to «in table body» and return.
If node is a caption element, then switch the
insertion mode to «in caption» and
return.
If node is a colgroup element, then switch the
insertion mode to «in column
group» and return.
If node is a table element, then switch the
insertion mode to «in table» and
return.
If node is a template element, then switch the
insertion mode to the current template insertion mode and
return.
If node is a head element and last is
false, then switch the insertion mode to «in
head» and return.
If node is a body element, then switch the
insertion mode to «in body» and
return.
If node is a frameset element, then switch the
insertion mode to «in frameset» and
return. (fragment case)
If node is an html element, run these substeps:
1. If the head element pointer is null, switch the
  insertion mode to «before head»
  and return. (fragment case)
2. Otherwise, the head element pointer is not null, switch the
  insertion mode to «after head» and
  return.
If last is true, then switch the insertion mode to «in body» and return. (fragment
case)
Let node now be the node before node in the
stack of open elements.
Return to the step labeled loop.

13.2.4.2 The stack of open elements

Initially, the stack of open elements is empty. The stack grows downwards; the
topmost node on the stack is the first one added to the stack, and the bottommost node of the
stack is the most recently added node in the stack (notwithstanding when the stack is manipulated
in a random access fashion as part of the handling for misnested
tags).

The «before html»
insertion mode creates the html document element, which is
then added to the stack.

In the fragment case, the stack of open elements is
initialized to contain an html element that is created as part of that algorithm. (The fragment case skips the
«before html» insertion mode.)

The html node, however it is created, is the topmost node of the stack. It only
gets popped off the stack when the parser finishes.

The current node is the bottommost node in this stack of open
elements.

The adjusted current node is the context
element if the parser was created as part of the HTML fragment parsing algorithm and
the stack of open elements has only one element in it (fragment case);
otherwise, the adjusted current node is the current node.

Elements in the stack of open elements fall into the following categories:

Special

The following elements have varying levels of special parsing rules: HTML’s
address, applet, area, article,
aside, base, basefont, bgsound,
blockquote, body, br, button,
caption, center, col, colgroup,
dd, details, dir, div, dl,
dt, embed, fieldset, figcaption,
figure, , form, frame,
frameset, h1, h2, h3, h4,
h5, h6, head, , hgroup,
hr, html, iframe,
img, input, keygen, li, link,
listing, main, marquee, ,
meta, nav, noembed, noframes,
noscript, object, ol, p, param,
plaintext, pre, script, section,
select, source, style, summary,
table, tbody, td, template,
textarea, tfoot, th, thead,
title, tr, track, ul, wbr,
xmp; MathML mi, MathML mo,
MathML mn, MathML ms, MathML
mtext, and MathML annotation-xml; and SVG
foreignObject, SVG desc, and SVG
title.

An image start tag token is handled by the tree builder,
but it is not in this list because it is not an element; it gets turned into an img
element.

Formatting

The following HTML elements are those that end up in the list of active formatting
elements: a, b, big, code,
em, font, i, nobr, s,
small, strike, strong, tt, and
u.

Ordinary

All other elements found while parsing an HTML document.

Typically, the special elements have the start and end tag tokens
handled specifically, while ordinary elements’ tokens fall into «any other start tag»
and «any other end tag» clauses, and some parts of the tree builder check if a particular element
in the stack of open elements is in the special category. However, some
elements (e.g., the option element) have their start or end tag tokens handled
specifically, but are still not in the special category, so that they get the
ordinary handling elsewhere.

The stack of open elements is said to have an element target node in a specific scope consisting of a
list of element types list when the following algorithm terminates in a match
state:

Initialize node to be the current node (the bottommost
node of the stack).
If node is the target node, terminate in a match state.
Otherwise, if node is one of the element types in list, terminate in a failure state.
Otherwise, set node to the previous entry in the stack of open
elements and return to step 2. (This will never fail, since the loop will always terminate
in the previous step if the top of the stack — an html element — is
reached.)

The stack of open elements is said to have a
particular element in scope when it has
that element in the specific scope consisting of the following element types:

applet
caption
html
table
td
th
marquee
object
template
MathML mi
MathML mo
MathML mn
MathML ms
MathML mtext
MathML annotation-xml
SVG foreignObject
SVG desc
SVG title

The stack of open elements is said to have a particular element in list item scope when it has that element in the specific scope consisting of the following
element types:

All the element types listed above for the has an element in scope algorithm.
ol in the HTML namespace
ul in the HTML namespace

The stack of open elements is said to have a particular element in button scope when it has that element in the specific scope consisting of the following element
types:

All the element types listed above for the has an element in scope algorithm.
button in the HTML namespace

The stack of open elements is said to have a particular element in table scope when it has that element in the specific scope consisting of the following element
types:

html in the HTML namespace
table in the HTML namespace
template in the HTML namespace

The stack of open elements is said to have a particular element in select scope when it has that element in the specific scope consisting of all element types
except the following:

optgroup in the HTML namespace
option in the HTML namespace

Nothing happens if at any time any of the elements in the stack of open elements
are moved to a new location in, or removed from, the Document tree. In particular,
the stack is not changed in this situation. This can cause, amongst other strange effects, content
to be appended to nodes that are no longer in the DOM.

In some cases (namely, when closing misnested formatting
elements), the stack is manipulated in a random-access fashion.

13.2.4.3 The list of active formatting elements

Initially, the list of active formatting elements is empty. It is used to handle
mis-nested formatting element tags.

The list contains elements in the formatting category, and markers. The markers are inserted when entering applet,
object, marquee, template, td,
th, and caption elements, and are used to prevent formatting from
«leaking» into applet, object, marquee,
template, td, th, and caption elements.

In addition, each element in the list of active formatting elements is associated
with the token for which it was created, so that further elements can be created for that token if
necessary.

When the steps below require the UA to push onto the list of active formatting
elements an element element, the UA must perform the following
steps:

If there are already three elements in the list of active formatting elements
after the last marker, if any, or anywhere in the
list if there are no markers, that have the same tag
name, namespace, and attributes as element, then remove the earliest such
element from the list of active formatting elements. For these purposes, the
attributes must be compared as they were when the elements were created by the parser; two
elements have the same attributes if all their parsed attributes can be paired such that the two
attributes in each pair have identical names, namespaces, and values (the order of the attributes
does not matter).

This is the Noah’s Ark clause. But with three per family instead of two.
Add element to the list of active formatting
elements.

When the steps below require the UA to reconstruct the active formatting elements,
the UA must perform the following steps:

If there are no entries in the list of active formatting elements, then there
is nothing to reconstruct; stop this algorithm.
If the last (most recently added) entry in the list of active formatting
elements is a marker, or if it is an element
that is in the stack of open elements, then there is nothing to reconstruct; stop
this algorithm.
Let entry be the last (most recently added) element in the list
of active formatting elements.
Rewind: If there are no entries before entry in the list
of active formatting elements, then jump to the step labeled create.
Let entry be the entry one earlier than entry in
the list of active formatting elements.
If entry is neither a marker nor an element that is also in the stack of
open elements, go to the step labeled rewind.
Advance: Let entry be the element one later than entry in the list of active formatting elements.
Create: Insert an HTML element for the token for which the element
entry was created, to obtain new element.
Replace the entry for entry in the list with an entry for new element.
If the entry for new element in the list of active formatting
elements is not the last entry in the list, return to the step labeled
advance.

This has the effect of reopening all the formatting elements that were opened in the current
body, cell, or caption (whichever is youngest) that haven’t been explicitly closed.

The way this specification is written, the list of active formatting
elements always consists of elements in chronological order with the least recently added
element first and the most recently added element last (except for while steps 7 to 10 of the
above algorithm are being executed, of course).

When the steps below require the UA to clear the list of active formatting elements up to
the last marker, the UA must perform the following steps:

Let entry be the last (most recently added) entry in the list of
active formatting elements.
Remove entry from the list of active formatting
elements.
If entry was a marker,
then stop the algorithm at this point. The list has been cleared up to the last marker.
Go to step 1.

13.2.4.4 The element pointers

Initially, the head element pointer and the form element pointer are both null.

Once a head element has been parsed (whether implicitly or explicitly) the
head element pointer gets set to point to this node.

The form element pointer points to the last
form element that was opened and whose end tag has not yet been seen. It is used to
make form controls associate with forms in the face of dramatically bad markup, for historical
reasons. It is ignored inside template elements.

13.2.4.5 Other parsing state flags

The scripting flag is set to «enabled» if scripting
was enabled for the Document with which the parser is associated when the
parser was created, and «disabled» otherwise.

The scripting flag can be enabled even when the parser was created as
part of the HTML fragment parsing algorithm, even though script elements
don’t execute in that case.

The frameset-ok flag is set to «ok» when the parser is created. It is set to «not
ok» after certain tokens are seen.

13.2.5 Tokenization

Implementations must act as if they used the following state machine to tokenize HTML. The
state machine must start in the data state. Most states consume a single character,
which may have various side-effects, and either switches the state machine to a new state to
reconsume the current input character, or switches it to a new state to
consume the next character, or stays in the same state
to consume the next character. Some states have more complicated behavior and can consume several
characters before switching to another state. In some cases, the tokenizer state is also changed
by the tree construction stage.

When a state says to reconsume a matched character in a specified state, that means
to switch to that state, but when it attempts to consume the next input character,
provide it with the current input character instead.

The exact behavior of certain states depends on the insertion mode and the
stack of open elements. Certain states also use a temporary buffer to track progress, and the character reference
state uses a return state to return to the
state it was invoked from.

The output of the tokenization step is a series of zero or more of the following tokens:
DOCTYPE, start tag, end tag, comment, character, end-of-file. DOCTYPE tokens have a name, a public
identifier, a system identifier, and a force-quirks flag. When a DOCTYPE token
is created, its name, public identifier, and system identifier must be marked as missing (which is
a distinct state from the empty string), and the force-quirks flag must be set to
off (its other state is on). Start and end tag tokens have a tag name, a self-closing flag, and a list of attributes, each of which has a
name and a value. When a start or end tag token is created, its self-closing flag must be unset (its other state is that it be set), and its attributes
list must be empty. Comment and character tokens have data.

When a token is emitted, it must immediately be handled by the tree construction
stage. The tree construction stage can affect the state of the tokenization stage, and can insert
additional characters into the stream. (For example, the script element can result in
scripts executing and using the dynamic markup insertion APIs to insert characters
into the stream being tokenized.)

Creating a token and emitting it are distinct actions. It is possible for a token
to be created but implicitly abandoned (never emitted), e.g. if the file ends unexpectedly while
processing the characters that are being parsed into a start tag token.

When a start tag token is emitted with its self-closing flag set, if the flag is not
acknowledged when it is processed by the tree
construction stage, that is a non-void-html-element-start-tag-with-trailing-solidus
parse error.

When an end tag token is emitted with attributes, that is an end-tag-with-attributes parse
error.

When an end tag token is emitted with its self-closing flag
set, that is an end-tag-with-trailing-solidus
parse error.

An appropriate end tag token is an end tag token whose tag name matches the tag name
of the last start tag to have been emitted from this tokenizer, if any. If no start tag has been
emitted from this tokenizer, then no end tag token is appropriate.

A character reference is said to be consumed as part of an attribute if the return state is either attribute value (double-quoted) state,
attribute value (single-quoted) state or attribute value (unquoted)
state.

When a state says to flush code points consumed as a character reference, it means
that for each code point in the temporary buffer (in the order they were added to the buffer) user agent must append the code point
from the buffer to the current attribute’s value if the character reference was consumed as part of an attribute, or emit the code point as a
character token otherwise.

Before each step of the tokenizer, the user agent must first check
the parser pause flag. If it is true, then the tokenizer must abort the processing of
any nested invocations of the tokenizer, yielding control back to the caller.

The tokenizer state machine consists of the states defined in the following subsections.

13.2.5.1 Data state

Consume the next input character:

U+0026 AMPERSAND (&): Set the return state to the data state.
Switch to the character reference state.
U+003C LESS-THAN SIGN (<): Switch to the tag open state.
U+0000 NULL: This is an unexpected-null-character parse
error. Emit the current input character as a character token.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.2 RCDATA state

Consume the next input character:

U+0026 AMPERSAND (&): Set the return state to the RCDATA state.
Switch to the character reference state.
U+003C LESS-THAN SIGN (<): Switch to the RCDATA less-than sign state.
U+0000 NULL: This is an unexpected-null-character parse
error. Emit a U+FFFD REPLACEMENT CHARACTER character token.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.3 RAWTEXT state

Consume the next input character:

U+003C LESS-THAN SIGN (<): Switch to the RAWTEXT less-than sign state.
U+0000 NULL: This is an unexpected-null-character parse
error. Emit a U+FFFD REPLACEMENT CHARACTER character token.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.4 Script data state

Consume the next input character:

U+003C LESS-THAN SIGN (<): Switch to the script data less-than sign state.
U+0000 NULL: This is an unexpected-null-character parse
error. Emit a U+FFFD REPLACEMENT CHARACTER character token.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.5 PLAINTEXT state

Consume the next input character:

U+0000 NULL: This is an unexpected-null-character parse
error. Emit a U+FFFD REPLACEMENT CHARACTER character token.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.6 Tag open state

Consume the next input character:

U+0021 EXCLAMATION MARK (!): Switch to the markup declaration open state.
U+002F SOLIDUS (/): Switch to the end tag open state.
ASCII alpha: Create a new start tag token, set its tag name to the empty string. Reconsume in
the tag name state.
U+003F QUESTION MARK (?): This is an unexpected-question-mark-instead-of-tag-name
parse error. Create a comment token whose data is the empty string.
Reconsume in the bogus comment state.
EOF: This is an eof-before-tag-name
parse error. Emit a U+003C LESS-THAN SIGN character token and an end-of-file
token.
Anything else: This is an invalid-first-character-of-tag-name
parse error. Emit a U+003C LESS-THAN SIGN character token. Reconsume in
the data state.

13.2.5.7 End tag open state

Consume the next input character:

ASCII alpha: Create a new end tag token, set its tag name to the empty string. Reconsume in
the tag name state.
U+003E GREATER-THAN SIGN (>): This is a missing-end-tag-name
parse error. Switch to the data state.
EOF: This is an eof-before-tag-name
parse error. Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS
character token and an end-of-file token.
Anything else: This is an invalid-first-character-of-tag-name
parse error. Create a comment token whose data is the empty string.
Reconsume in the bogus comment state.

13.2.5.8 Tag name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current tag token.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current tag token’s tag name.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current tag token’s tag
name.
EOF: This is an eof-in-tag parse error.
Emit an end-of-file token.
Anything else: Append the current input character to the current tag token’s tag name.

13.2.5.9 RCDATA less-than sign state

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to
the RCDATA end tag open state.
Anything else: Emit a U+003C LESS-THAN SIGN character token. Reconsume in the RCDATA
state.

13.2.5.10 RCDATA end tag open state

Consume the next input character:

ASCII alpha: Create a new end tag token, set its tag name to the empty string. Reconsume in
the RCDATA end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and a U+002F SOLIDUS character token.
Reconsume in the RCDATA state.

13.2.5.11 RCDATA end tag name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the
before attribute name state. Otherwise, treat it as per the «anything else» entry
below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the
self-closing start tag state. Otherwise, treat it as per the «anything else» entry
below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then switch to the
data state and emit the current tag token. Otherwise, treat it as per the «anything
else» entry below.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current tag token’s tag name. Append the current input
character to the temporary buffer.
ASCII lower alpha: Append the current input character to the current tag token’s tag name. Append
the current input character to the temporary buffer.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and a
character token for each of the characters in the temporary buffer (in the order they were added to the buffer). Reconsume in the
RCDATA state.

13.2.5.12 RAWTEXT less-than sign state

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to
the RAWTEXT end tag open state.
Anything else: Emit a U+003C LESS-THAN SIGN character token. Reconsume in the RAWTEXT
state.

13.2.5.13 RAWTEXT end tag open state

Consume the next input character:

ASCII alpha: Create a new end tag token, set its tag name to the empty string. Reconsume in
the RAWTEXT end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and a U+002F SOLIDUS character token.
Reconsume in the RAWTEXT state.

13.2.5.14 RAWTEXT end tag name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the
before attribute name state. Otherwise, treat it as per the «anything else» entry
below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the
self-closing start tag state. Otherwise, treat it as per the «anything else» entry
below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then switch to the
data state and emit the current tag token. Otherwise, treat it as per the «anything
else» entry below.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current tag token’s tag name. Append the current input
character to the temporary buffer.
ASCII lower alpha: Append the current input character to the current tag token’s tag name. Append
the current input character to the temporary buffer.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and a
character token for each of the characters in the temporary buffer (in the order they were added to the buffer). Reconsume in the
RAWTEXT state.

13.2.5.15 Script data less-than sign state

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to
the script data end tag open state.
U+0021 EXCLAMATION MARK (!): Switch to the script data escape start state. Emit a U+003C LESS-THAN SIGN
character token and a U+0021 EXCLAMATION MARK character token.
Anything else: Emit a U+003C LESS-THAN SIGN character token. Reconsume in the script data
state.

13.2.5.16 Script data end tag open state

Consume the next input character:

ASCII alpha: Create a new end tag token, set its tag name to the empty string. Reconsume in
the script data end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and a U+002F SOLIDUS character token.
Reconsume in the script data state.

13.2.5.17 Script data end tag name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the
before attribute name state. Otherwise, treat it as per the «anything else» entry
below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the
self-closing start tag state. Otherwise, treat it as per the «anything else» entry
below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then switch to the
data state and emit the current tag token. Otherwise, treat it as per the «anything
else» entry below.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current tag token’s tag name. Append the current input
character to the temporary buffer.
ASCII lower alpha: Append the current input character to the current tag token’s tag name. Append
the current input character to the temporary buffer.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and a
character token for each of the characters in the temporary buffer (in the order they were added to the buffer). Reconsume in the
script data state.

13.2.5.18 Script data escape start state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the script data escape start dash state. Emit a U+002D HYPHEN-MINUS
character token.
Anything else: Reconsume in the script data state.

13.2.5.19 Script data escape start dash state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the script data escaped dash dash state. Emit a U+002D HYPHEN-MINUS
character token.
Anything else: Reconsume in the script data state.

13.2.5.20 Script data escaped state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the script data escaped dash state. Emit a U+002D HYPHEN-MINUS
character token.
U+003C LESS-THAN SIGN (<): Switch to the script data escaped less-than sign state.
U+0000 NULL: This is an unexpected-null-character parse
error. Emit a U+FFFD REPLACEMENT CHARACTER character token.
EOF: This is an eof-in-script-html-comment-like-text
parse error. Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.21 Script data escaped dash state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the script data escaped dash dash state. Emit a U+002D HYPHEN-MINUS
character token.
U+003C LESS-THAN SIGN (<): Switch to the script data escaped less-than sign state.
U+0000 NULL: This is an unexpected-null-character parse
error. Switch to the script data escaped state. Emit a U+FFFD REPLACEMENT
CHARACTER character token.
EOF: This is an eof-in-script-html-comment-like-text
parse error. Emit an end-of-file token.
Anything else: Switch to the script data escaped state. Emit the current input
character as a character token.

13.2.5.22 Script data escaped dash dash state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token.
U+003C LESS-THAN SIGN (<): Switch to the script data escaped less-than sign state.
U+003E GREATER-THAN SIGN (>): Switch to the script data state. Emit a U+003E GREATER-THAN SIGN character
token.
U+0000 NULL: This is an unexpected-null-character parse
error. Switch to the script data escaped state. Emit a U+FFFD REPLACEMENT
CHARACTER character token.
EOF: This is an eof-in-script-html-comment-like-text
parse error. Emit an end-of-file token.
Anything else: Switch to the script data escaped state. Emit the current input
character as a character token.

13.2.5.23 Script data escaped less-than sign state

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to
the script data escaped end tag open state.
ASCII alpha: Set the temporary buffer to the empty string. Emit a
U+003C LESS-THAN SIGN character token. Reconsume in the script data double
escape start state.
Anything else: Emit a U+003C LESS-THAN SIGN character token. Reconsume in the script data
escaped state.

13.2.5.24 Script data escaped end tag open state

Consume the next input character:

ASCII alpha: Create a new end tag token, set its tag name to the empty string. Reconsume in
the script data escaped end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and a U+002F SOLIDUS character token.
Reconsume in the script data escaped state.

13.2.5.25 Script data escaped end tag name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the
before attribute name state. Otherwise, treat it as per the «anything else» entry
below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the
self-closing start tag state. Otherwise, treat it as per the «anything else» entry
below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then switch to the
data state and emit the current tag token. Otherwise, treat it as per the «anything
else» entry below.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current tag token’s tag name. Append the current input
character to the temporary buffer.
ASCII lower alpha: Append the current input character to the current tag token’s tag name. Append
the current input character to the temporary buffer.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and a
character token for each of the characters in the temporary buffer (in the order they were added to the buffer). Reconsume in the script
data escaped state.

13.2.5.26 Script data double escape start state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE
U+002F SOLIDUS (/)
U+003E GREATER-THAN SIGN (>): If the temporary buffer is the string «script«, then switch to the script data double escaped state.
Otherwise, switch to the script data escaped state. Emit the current input
character as a character token.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the temporary buffer. Emit the
current input character as a character token.
ASCII lower alpha: Append the current input character to the temporary buffer. Emit the current input character as a character
token.
Anything else: Reconsume in the script data escaped state.

13.2.5.27 Script data double escaped state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the script data double escaped dash state. Emit a U+002D HYPHEN-MINUS
character token.
U+003C LESS-THAN SIGN (<): Switch to the script data double escaped less-than sign state. Emit a U+003C
LESS-THAN SIGN character token.
U+0000 NULL: This is an unexpected-null-character parse
error. Emit a U+FFFD REPLACEMENT CHARACTER character token.
EOF: This is an eof-in-script-html-comment-like-text
parse error. Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

13.2.5.28 Script data double escaped dash state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the script data double escaped dash dash state. Emit a U+002D
HYPHEN-MINUS character token.
U+003C LESS-THAN SIGN (<): Switch to the script data double escaped less-than sign state. Emit a U+003C
LESS-THAN SIGN character token.
U+0000 NULL: This is an unexpected-null-character parse
error. Switch to the script data double escaped state. Emit a U+FFFD
REPLACEMENT CHARACTER character token.
EOF: This is an eof-in-script-html-comment-like-text
parse error. Emit an end-of-file token.
Anything else: Switch to the script data double escaped state. Emit the current input
character as a character token.

13.2.5.29 Script data double escaped dash dash state

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token.
U+003C LESS-THAN SIGN (<): Switch to the script data double escaped less-than sign state. Emit a U+003C
LESS-THAN SIGN character token.
U+003E GREATER-THAN SIGN (>): Switch to the script data state. Emit a U+003E GREATER-THAN SIGN character
token.
U+0000 NULL: This is an unexpected-null-character parse
error. Switch to the script data double escaped state. Emit a U+FFFD
REPLACEMENT CHARACTER character token.
EOF: This is an eof-in-script-html-comment-like-text
parse error. Emit an end-of-file token.
Anything else: Switch to the script data double escaped state. Emit the current input
character as a character token.

13.2.5.30 Script data double escaped less-than sign state

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to
the script data double escape end state. Emit a U+002F SOLIDUS character token.
Anything else: Reconsume in the script data double escaped state.

13.2.5.31 Script data double escape end state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE
U+002F SOLIDUS (/)
U+003E GREATER-THAN SIGN (>): If the temporary buffer is the string «script«, then switch to the script data escaped state. Otherwise,
switch to the script data double escaped state. Emit the current input
character as a character token.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the temporary buffer. Emit the
current input character as a character token.
ASCII lower alpha: Append the current input character to the temporary buffer. Emit the current input character as a character
token.
Anything else: Reconsume in the script data double escaped state.

13.2.5.32 Before attribute name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+002F SOLIDUS (/)
U+003E GREATER-THAN SIGN (>)
EOF: Reconsume in the after attribute name state.
U+003D EQUALS SIGN (=): This is an unexpected-equals-sign-before-attribute-name
parse error. Start a new attribute in the current tag token. Set that attribute’s
name to the current input character, and its value to the empty string. Switch to
the attribute name state.
Anything else: Start a new attribute in the current tag token. Set that attribute name and value to the
empty string. Reconsume in the attribute name state.

13.2.5.33 Attribute name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE
U+002F SOLIDUS (/)
U+003E GREATER-THAN SIGN (>)
EOF: Reconsume in the after attribute name state.
U+003D EQUALS SIGN (=): Switch to the before attribute value state.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current attribute’s name.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current attribute’s
name.
U+0022 QUOTATION MARK («)
U+0027 APOSTROPHE (‘)
U+003C LESS-THAN SIGN (<): This is an unexpected-character-in-attribute-name
parse error. Treat it as per the «anything else» entry below.
Anything else: Append the current input character to the current attribute’s name.

When the user agent leaves the attribute name state (and before emitting the tag token, if
appropriate), the complete attribute’s name must be compared to the other attributes on the same
token; if there is already an attribute on the token with the exact same name, then this is a
duplicate-attribute parse error
and the new attribute must be removed from the token.

If an attribute is so removed from a token, it, and the value that gets associated
with it, if any, are never subsequently used by the parser, and are therefore effectively
discarded. Removing the attribute in this way does not change its status as the «current
attribute» for the purposes of the tokenizer, however.

13.2.5.34 After attribute name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003D EQUALS SIGN (=): Switch to the before attribute value state.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current tag token.
EOF: This is an eof-in-tag
parse error. Emit an end-of-file token.
Anything else: Start a new attribute in the current tag token. Set that attribute name and value to the
empty string. Reconsume in the attribute name state.

13.2.5.35 Before attribute value state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+0022 QUOTATION MARK («): Switch to the attribute value (double-quoted) state.
U+0027 APOSTROPHE (‘): Switch to the attribute value (single-quoted) state.
U+003E GREATER-THAN SIGN (>): This is a missing-attribute-value
parse error. Switch to the data state. Emit the current tag token.
Anything else: Reconsume in the attribute value (unquoted) state.

13.2.5.36 Attribute value (double-quoted) state

Consume the next input character:

U+0022 QUOTATION MARK («): Switch to the after attribute value (quoted) state.
U+0026 AMPERSAND (&): Set the return state to the attribute value
(double-quoted) state. Switch to the character reference state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current attribute’s
value.
EOF: This is an eof-in-tag parse error.
Emit an end-of-file token.
Anything else: Append the current input character to the current attribute’s value.

13.2.5.37 Attribute value (single-quoted) state

Consume the next input character:

U+0027 APOSTROPHE (‘): Switch to the after attribute value (quoted) state.
U+0026 AMPERSAND (&): Set the return state to the attribute value
(single-quoted) state. Switch to the character reference state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current attribute’s
value.
EOF: This is an eof-in-tag parse error.
Emit an end-of-file token.
Anything else: Append the current input character to the current attribute’s value.

13.2.5.38 Attribute value (unquoted) state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before attribute name state.
U+0026 AMPERSAND (&): Set the return state to the attribute value
(unquoted) state. Switch to the character reference state.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current tag token.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current attribute’s
value.
U+0022 QUOTATION MARK («)
U+0027 APOSTROPHE (‘)
U+003C LESS-THAN SIGN (<)
U+003D EQUALS SIGN (=)
U+0060 GRAVE ACCENT (`): This is an unexpected-character-in-unquoted-attribute-value
parse error. Treat it as per the «anything else» entry below.
EOF: This is an eof-in-tag
parse error. Emit an end-of-file token.
Anything else: Append the current input character to the current attribute’s value.

13.2.5.39 After attribute value (quoted) state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current tag token.
EOF: This is an eof-in-tag parse error.
Emit an end-of-file token.
Anything else: This is a missing-whitespace-between-attributes
parse error. Reconsume in the before attribute name state.

13.2.5.40 Self-closing start tag state

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Set the self-closing flag of the current tag token. Switch
to the data state. Emit the current tag token.
EOF: This is an eof-in-tag
parse error. Emit an end-of-file token.
Anything else: This is an unexpected-solidus-in-tag parse
error. Reconsume in the before attribute name state.

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current comment token.
EOF: Emit the comment. Emit an end-of-file token.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the comment token’s data.
Anything else: Append the current input character to the comment token’s data.

13.2.5.42 Markup declaration open state

If the next few characters are:

Two U+002D HYPHEN-MINUS characters (-): Consume those two characters, create a comment token whose data is the empty string, and
switch to the comment start state.
ASCII case-insensitive match for the word «DOCTYPE»: Consume those characters and switch to the DOCTYPE state.
The string «[CDATA[» (the five uppercase letters «CDATA» with a U+005B LEFT SQUARE BRACKET character before and after): Consume those characters. If there is an adjusted current node and it is not
an element in the HTML namespace, then switch to the CDATA section
state. Otherwise, this is a cdata-in-html-content parse
error. Create a comment token whose data is the «[CDATA[» string. Switch to the
bogus comment state.
Anything else: This is an incorrectly-opened-comment
parse error. Create a comment token whose data is the empty string. Switch to the
bogus comment state (don’t consume anything in the current state).

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment start dash state.
U+003E GREATER-THAN SIGN (>): This is an abrupt-closing-of-empty-comment parse
error. Switch to the data state. Emit the current comment token.
Anything else: Reconsume in the comment state.

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment end state.
U+003E GREATER-THAN SIGN (>): This is an abrupt-closing-of-empty-comment parse
error. Switch to the data state. Emit the current comment token.
EOF: This is an eof-in-comment parse
error. Emit the current comment token. Emit an end-of-file token.
Anything else: Append a U+002D HYPHEN-MINUS character (-) to the comment token’s data.
Reconsume in the comment state.

Consume the next input character:

U+003C LESS-THAN SIGN (<): Append the current input character to the comment token’s data. Switch to the
comment less-than sign state.
U+002D HYPHEN-MINUS (-): Switch to the comment end dash state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the comment token’s data.
EOF: This is an eof-in-comment parse
error. Emit the current comment token. Emit an end-of-file token.
Anything else: Append the current input character to the comment token’s data.

Consume the next input character:

U+0021 EXCLAMATION MARK (!): Append the current input character to the comment token’s data. Switch to the
comment less-than sign bang state.
U+003C LESS-THAN SIGN (<): Append the current input character to the comment token’s data.
Anything else: Reconsume in the comment state.

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment less-than sign bang dash state.
Anything else: Reconsume in the comment state.

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment less-than sign bang dash dash state.
Anything else: Reconsume in the comment end dash state.

Consume the next input character:

U+003E GREATER-THAN SIGN (>)
EOF: Reconsume in the comment end state.
Anything else: This is a nested-comment parse
error. Reconsume in the comment end state.

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment end state.
EOF: This is an eof-in-comment parse
error. Emit the current comment token. Emit an end-of-file token.
Anything else: Append a U+002D HYPHEN-MINUS character (-) to the comment token’s data.
Reconsume in the comment state.

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current comment token.
U+0021 EXCLAMATION MARK (!): Switch to the comment end bang state.
U+002D HYPHEN-MINUS (-): Append a U+002D HYPHEN-MINUS character (-) to the comment token’s data.
EOF: This is an eof-in-comment parse
error. Emit the current comment token. Emit an end-of-file token.
Anything else: Append two U+002D HYPHEN-MINUS characters (-) to the comment token’s data.
Reconsume in the comment state.

Consume the next input character:

U+002D HYPHEN-MINUS (-): Append two U+002D HYPHEN-MINUS characters (-) and a U+0021 EXCLAMATION MARK character (!) to
the comment token’s data. Switch to the comment end dash state.
U+003E GREATER-THAN SIGN (>): This is an incorrectly-closed-comment parse
error. Switch to the data state. Emit the current comment token.
EOF: This is an eof-in-comment parse
error. Emit the current comment token. Emit an end-of-file token.
Anything else: Append two U+002D HYPHEN-MINUS characters (-) and a U+0021 EXCLAMATION MARK character (!) to
the comment token’s data. Reconsume in the comment state.

13.2.5.53 DOCTYPE state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before DOCTYPE name state.
U+003E GREATER-THAN SIGN (>): Reconsume in the before DOCTYPE name state.
EOF: This is an eof-in-doctype parse
error. Create a new DOCTYPE token. Set its force-quirks
flag to on. Emit the current token. Emit an end-of-file token.
Anything else: This is a missing-whitespace-before-doctype-name
parse error. Reconsume in the before DOCTYPE name state.

13.2.5.54 Before DOCTYPE name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
ASCII upper alpha: Create a new DOCTYPE token. Set the token’s name to the lowercase version of the
current input character (add 0x0020 to the character’s code point). Switch to the
DOCTYPE name state.
U+0000 NULL: This is an unexpected-null-character parse
error. Create a new DOCTYPE token. Set the token’s name to a U+FFFD REPLACEMENT CHARACTER
character. Switch to the DOCTYPE name state.
U+003E GREATER-THAN SIGN (>): This is a missing-doctype-name
parse error. Create a new DOCTYPE token. Set its force-quirks flag to on. Switch to the data
state. Emit the current token.
EOF: This is an eof-in-doctype parse
error. Create a new DOCTYPE token. Set its force-quirks
flag to on. Emit the current token. Emit an end-of-file token.
Anything else: Create a new DOCTYPE token. Set the token’s name to the current input character.
Switch to the DOCTYPE name state.

13.2.5.55 DOCTYPE name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the after DOCTYPE name state.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current DOCTYPE token.
ASCII upper alpha: Append the lowercase version of the current input character (add 0x0020 to the
character’s code point) to the current DOCTYPE token’s name.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current DOCTYPE token’s
name.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: Append the current input character to the current DOCTYPE token’s name.

13.2.5.56 After DOCTYPE name state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)

U+000A LINE FEED (LF)

U+000C FORM FEED (FF)

U+0020 SPACE

Ignore the character.

U+003E GREATER-THAN SIGN (>)

Switch to the data state. Emit the current DOCTYPE token.

EOF

This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.

Anything else

If the six characters starting from the current input character are an
ASCII case-insensitive match for the word «PUBLIC», then consume those characters
and switch to the after DOCTYPE public keyword state.

Otherwise, if the six characters starting from the current input character are
an ASCII case-insensitive match for the word «SYSTEM», then consume those
characters and switch to the after DOCTYPE system keyword state.

Otherwise, this is an invalid-character-sequence-after-doctype-name
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.57 After DOCTYPE public keyword state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before DOCTYPE public identifier state.
U+0022 QUOTATION MARK («): This is a missing-whitespace-after-doctype-public-keyword
parse error. Set the current DOCTYPE token’s public identifier to the empty string (not
missing), then switch to the DOCTYPE public identifier (double-quoted) state.
U+0027 APOSTROPHE (‘): This is a missing-whitespace-after-doctype-public-keyword
parse error. Set the current DOCTYPE token’s public identifier to the empty string (not
missing), then switch to the DOCTYPE public identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): This is a missing-doctype-public-identifier parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is a missing-quote-before-doctype-public-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.58 Before DOCTYPE public identifier state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+0022 QUOTATION MARK («): Set the current DOCTYPE token’s public identifier to the empty string (not missing), then switch to
the DOCTYPE public identifier (double-quoted) state.
U+0027 APOSTROPHE (‘): Set the current DOCTYPE token’s public identifier to the empty string (not missing), then switch to
the DOCTYPE public identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): This is a missing-doctype-public-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is a missing-quote-before-doctype-public-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.59 DOCTYPE public identifier (double-quoted) state

Consume the next input character:

U+0022 QUOTATION MARK («): Switch to the after DOCTYPE public identifier state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current DOCTYPE token’s
public identifier.
U+003E GREATER-THAN SIGN (>): This is an abrupt-doctype-public-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: Append the current input character to the current DOCTYPE token’s public
identifier.

13.2.5.60 DOCTYPE public identifier (single-quoted) state

Consume the next input character:

U+0027 APOSTROPHE (‘): Switch to the after DOCTYPE public identifier state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current DOCTYPE token’s
public identifier.
U+003E GREATER-THAN SIGN (>): This is an abrupt-doctype-public-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: Append the current input character to the current DOCTYPE token’s public
identifier.

13.2.5.61 After DOCTYPE public identifier state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the between DOCTYPE public and system identifiers state.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current DOCTYPE token.
U+0022 QUOTATION MARK («): This is a missing-whitespace-between-doctype-public-and-system-identifiers
parse error. Set the current DOCTYPE token’s system identifier to the empty string (not
missing), then switch to the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE (‘): This is a missing-whitespace-between-doctype-public-and-system-identifiers
parse error. Set the current DOCTYPE token’s system identifier to the empty string (not
missing), then switch to the DOCTYPE system identifier (single-quoted) state.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is a missing-quote-before-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.62 Between DOCTYPE public and system identifiers state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current DOCTYPE token.
U+0022 QUOTATION MARK («): Set the current DOCTYPE token’s system identifier to the empty string (not missing), then switch to
the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE (‘): Set the current DOCTYPE token’s system identifier to the empty string (not missing), then switch to
the DOCTYPE system identifier (single-quoted) state.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is a missing-quote-before-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.63 After DOCTYPE system keyword state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before DOCTYPE system identifier state.
U+0022 QUOTATION MARK («): This is a missing-whitespace-after-doctype-system-keyword
parse error. Set the current DOCTYPE token’s system identifier to the empty string (not
missing), then switch to the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE (‘): This is a missing-whitespace-after-doctype-system-keyword
parse error. Set the current DOCTYPE token’s system identifier to the empty string (not
missing), then switch to the DOCTYPE system identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): This is a missing-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is a missing-quote-before-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.64 Before DOCTYPE system identifier state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+0022 QUOTATION MARK («): Set the current DOCTYPE token’s system identifier to the empty string (not missing), then switch to
the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE (‘): Set the current DOCTYPE token’s system identifier to the empty string (not missing), then switch to
the DOCTYPE system identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): This is a missing-doctype-system-identifier parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is a missing-quote-before-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Reconsume in the bogus DOCTYPE state.

13.2.5.65 DOCTYPE system identifier (double-quoted) state

Consume the next input character:

U+0022 QUOTATION MARK («): Switch to the after DOCTYPE system identifier state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current DOCTYPE token’s
system identifier.
U+003E GREATER-THAN SIGN (>): This is an abrupt-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: Append the current input character to the current DOCTYPE token’s system
identifier.

13.2.5.66 DOCTYPE system identifier (single-quoted) state

Consume the next input character:

U+0027 APOSTROPHE (‘): Switch to the after DOCTYPE system identifier state.
U+0000 NULL: This is an unexpected-null-character parse
error. Append a U+FFFD REPLACEMENT CHARACTER character to the current DOCTYPE token’s
system identifier.
U+003E GREATER-THAN SIGN (>): This is an abrupt-doctype-system-identifier
parse error. Set the current DOCTYPE token’s force-quirks
flag to on. Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: Append the current input character to the current DOCTYPE token’s system
identifier.

13.2.5.67 After DOCTYPE system identifier state

Consume the next input character:

U+0009 CHARACTER TABULATION (tab)
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Ignore the character.
U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the current DOCTYPE token.
EOF: This is an eof-in-doctype parse
error. Set the current DOCTYPE token’s force-quirks flag to
on. Emit the current DOCTYPE token. Emit an end-of-file token.
Anything else: This is an unexpected-character-after-doctype-system-identifier
parse error. Reconsume in the bogus DOCTYPE state. (This
does not set the current DOCTYPE token’s force-quirks flag to
on.)

13.2.5.68 Bogus DOCTYPE state

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Switch to the data state. Emit the DOCTYPE token.
U+0000 NULL: This is an unexpected-null-character parse
error. Ignore the character.
EOF: Emit the DOCTYPE token. Emit an end-of-file token.
Anything else: Ignore the character.

13.2.5.69 CDATA section state

Consume the next input character:

U+005D RIGHT SQUARE BRACKET (]): Switch to the CDATA section bracket state.
EOF: This is an eof-in-cdata parse
error. Emit an end-of-file token.
Anything else: Emit the current input character as a character token.

U+0000 NULL characters are handled in the tree construction stage, as part of the
in foreign content insertion mode, which
is the only place where CDATA sections can appear.

13.2.5.70 CDATA section bracket state

Consume the next input character:

U+005D RIGHT SQUARE BRACKET (]): Switch to the CDATA section end state.
Anything else: Emit a U+005D RIGHT SQUARE BRACKET character token. Reconsume in the
CDATA section state.

13.2.5.71 CDATA section end state

Consume the next input character:

U+005D RIGHT SQUARE BRACKET (]): Emit a U+005D RIGHT SQUARE BRACKET character token.
U+003E GREATER-THAN SIGN character: Switch to the data state.
Anything else: Emit two U+005D RIGHT SQUARE BRACKET character tokens. Reconsume in the
CDATA section state.

13.2.5.72 Character reference state

Set the temporary buffer to the empty string. Append
a U+0026 AMPERSAND (&) character to the temporary buffer. Consume the next input character:

ASCII alphanumeric: Reconsume in the named character reference state.
U+0023 NUMBER SIGN (#): Append the current input character to the
temporary buffer. Switch to the numeric character
reference state.
Anything else: Flush code points consumed as a character reference. Reconsume in
the return state.

13.2.5.73 Named character reference state

Consume the maximum number of characters possible, where the consumed characters are one of the
identifiers in the first column of the named character references table. Append each
character to the temporary buffer when it’s consumed.

If there is a match

If the character reference was consumed as part of an
attribute, and the last character matched is not a U+003B SEMICOLON character (;), and
the next input character is either a U+003D EQUALS SIGN character (=) or an
ASCII alphanumeric, then, for historical reasons, flush code points consumed
as a character reference and switch to the return state.

Otherwise:

If the last character matched is not a U+003B SEMICOLON character (;), then this is a
missing-semicolon-after-character-reference
parse error.
Set the temporary buffer to the empty string.
Append one or two characters corresponding to the character reference name (as given by the
second column of the named character references table) to the temporary buffer.
Flush code points consumed as a character reference. Switch to the return state.

Otherwise

Flush code points consumed as a character reference. Switch to the
ambiguous ampersand state.

If the markup contains (not in an attribute) the string I'm &notit; I tell you, the character reference is parsed as «not», as in, I'm ¬it; I tell you (and this is a parse error). But if the markup was I'm ∉ I tell you, the character reference would be parsed as «notin;», resulting
in I'm ∉ I tell you (and no parse error).

However, if the markup contains the string I'm &notit; I tell you
in an attribute, no character reference is parsed and string remains intact (and there is no
parse error).

13.2.5.74 Ambiguous ampersand state

Consume the next input character:

ASCII alphanumeric: If the character reference was consumed as part of an
attribute, then append the current input character to the current
attribute’s value. Otherwise, emit the current input character as a character
token.
U+003B SEMICOLON (;): This is an unknown-named-character-reference
parse error. Reconsume in the return state.
Anything else: Reconsume in the return state.

13.2.5.75 Numeric character reference state

Set the character reference code to
zero (0).

Consume the next input character:

U+0078 LATIN SMALL LETTER X
U+0058 LATIN CAPITAL LETTER X: Append the current input character to the temporary buffer. Switch to the hexadecimal character reference start
state.
Anything else: Reconsume in the decimal character reference start state.

13.2.5.76 Hexadecimal character reference start state

Consume the next input character:

ASCII hex digit: Reconsume in the hexadecimal character reference state.
Anything else: This is an absence-of-digits-in-numeric-character-reference
parse error. Flush code points consumed as a character reference.
Reconsume in the return state.

13.2.5.77 Decimal character reference start state

Consume the next input character:

ASCII digit: Reconsume in the decimal character reference state.
Anything else: This is an absence-of-digits-in-numeric-character-reference
parse error. Flush code points consumed as a character reference.
Reconsume in the return state.

13.2.5.78 Hexadecimal character reference state

Consume the next input character:

ASCII digit: Multiply the character reference code by 16.
Add a numeric version of the current input character (subtract 0x0030 from the
character’s code point) to the character reference code.
ASCII upper hex digit: Multiply the character reference code by 16.
Add a numeric version of the current input character as a hexadecimal digit
(subtract 0x0037 from the character’s code point) to the character reference code.
ASCII lower hex digit: Multiply the character reference code by 16.
Add a numeric version of the current input character as a hexadecimal digit
(subtract 0x0057 from the character’s code point) to the character reference code.
U+003B SEMICOLON: Switch to the numeric character reference end state.
Anything else: This is a missing-semicolon-after-character-reference
parse error. Reconsume in the numeric character reference end
state.

13.2.5.79 Decimal character reference state

Consume the next input character:

ASCII digit: Multiply the character reference code by 10.
Add a numeric version of the current input character (subtract 0x0030 from the
character’s code point) to the character reference code.
U+003B SEMICOLON: Switch to the numeric character reference end state.
Anything else: This is a missing-semicolon-after-character-reference
parse error. Reconsume in the numeric character reference end
state.

13.2.5.80 Numeric character reference end state

Check the character reference code:

If the number is 0x00, then this is a null-character-reference parse
error. Set the character reference code to
0xFFFD.
If the number is greater than 0x10FFFF, then this is a character-reference-outside-unicode-range
parse error. Set the character reference code to 0xFFFD.
If the number is a surrogate, then this is a surrogate-character-reference
parse error. Set the character reference code to 0xFFFD.
If the number is a noncharacter, then this is a
noncharacter-character-reference
parse error.

If the number is 0x0D, or a
control that’s not ASCII whitespace, then this is a
control-character-reference
parse error. If the number is one of the numbers in the first column of the
following table, then find the row with that number in the first column, and set the character reference code to the number in the second
column of that row.

Number	Code point
0x80	0x20AC	EURO SIGN (€)
0x82	0x201A	SINGLE LOW-9 QUOTATION MARK (‚)
0x83	0x0192	LATIN SMALL LETTER F WITH HOOK (ƒ)
0x84	0x201E	DOUBLE LOW-9 QUOTATION MARK („)
0x85	0x2026	HORIZONTAL ELLIPSIS (…)
0x86	0x2020	DAGGER (†)
0x87	0x2021	DOUBLE DAGGER (‡)
0x88	0x02C6	MODIFIER LETTER CIRCUMFLEX ACCENT (ˆ)
0x89	0x2030	PER MILLE SIGN (‰)
0x8A	0x0160	LATIN CAPITAL LETTER S WITH CARON (Š)
0x8B	0x2039	SINGLE LEFT-POINTING ANGLE QUOTATION MARK (‹)
0x8C	0x0152	LATIN CAPITAL LIGATURE OE (Œ)
0x8E	0x017D	LATIN CAPITAL LETTER Z WITH CARON (Ž)
0x91	0x2018	LEFT SINGLE QUOTATION MARK (‘)
0x92	0x2019	RIGHT SINGLE QUOTATION MARK (’)
0x93	0x201C	LEFT DOUBLE QUOTATION MARK (“)
0x94	0x201D	RIGHT DOUBLE QUOTATION MARK (”)
0x95	0x2022	BULLET (•)
0x96	0x2013	EN DASH (–)
0x97	0x2014	EM DASH (—)
0x98	0x02DC	SMALL TILDE (˜)
0x99	0x2122	TRADE MARK SIGN (™)
0x9A	0x0161	LATIN SMALL LETTER S WITH CARON (š)
0x9B	0x203A	SINGLE RIGHT-POINTING ANGLE QUOTATION MARK (›)
0x9C	0x0153	LATIN SMALL LIGATURE OE (œ)
0x9E	0x017E	LATIN SMALL LETTER Z WITH CARON (ž)
0x9F	0x0178	LATIN CAPITAL LETTER Y WITH DIAERESIS (Ÿ)

Set the temporary buffer to the empty string. Append a
code point equal to the character reference code to
the temporary buffer. Flush code points consumed as a
character reference. Switch to the return state.

13.2.6 Tree construction

The input to the tree construction stage is a sequence of tokens from the
tokenization stage. The tree construction stage is associated with a DOM
Document object when a parser is created. The «output» of this stage consists of
dynamically modifying or extending that document’s DOM tree.

This specification does not define when an interactive user agent has to render the
Document so that it is available to the user, or when it has to begin accepting user
input.

As each token is emitted from the tokenizer, the user agent must follow the appropriate steps
from the following list, known as the tree construction dispatcher:

If the stack of open elements is empty
If the adjusted current node is an element in the HTML namespace
If the adjusted current node is a MathML text integration point and the token is a start tag whose tag name is neither «mglyph» nor «malignmark»
If the adjusted current node is a MathML text integration point and the token is a character token
If the adjusted current node is a MathML annotation-xml element and the token is a start tag whose tag name is «svg»
If the adjusted current node is an HTML integration point and the token is a start tag
If the adjusted current node is an HTML integration point and the token is a character token
If the token is an end-of-file token: Process the token according to the rules given in the section corresponding to the current
insertion mode in HTML content.
Otherwise: Process the token according to the rules given in the section for parsing tokens in foreign content.

The next token is the token that is about to be processed by the tree
construction dispatcher (even if the token is subsequently just ignored).

A node is a MathML text integration point if it is one of the following
elements:

A MathML mi element
A MathML mo element
A MathML mn element
A MathML ms element
A MathML mtext element

A node is an HTML integration point if it is one of the following elements:

A MathML annotation-xml element whose start tag token had an
attribute with the name «encoding» whose value was an ASCII case-insensitive match
for the string «text/html«
A MathML annotation-xml element whose start tag token had an
attribute with the name «encoding» whose value was an ASCII case-insensitive match
for the string «application/xhtml+xml«
An SVG foreignObject element
An SVG desc element
An SVG title element

If the node in question is the context element passed to the HTML fragment
parsing algorithm, then the start tag token for that element is the «fake» token created
during by that HTML fragment parsing algorithm.

Not all of the tag names mentioned below are conformant tag names in this
specification; many are included to handle legacy content. They still form part of the algorithm
that implementations are required to implement to claim conformance.

The algorithm described below places no limit on the depth of the DOM tree
generated, or on the length of tag names, attribute names, attribute values, Text
nodes, etc. While implementers are encouraged to avoid arbitrary limits, it is
recognized that practical concerns will likely force user agents to impose nesting depth
constraints.

13.2.6.1 Creating and inserting nodes

While the parser is processing a token, it can enable or disable foster parenting. This affects the following algorithm.

The appropriate place for inserting a node, optionally using a particular
override target, is the position in an element returned by running the following steps:

If there was an override target specified, then let target be the
override target.

Otherwise, let target be the current node.
Determine the adjusted insertion location using the first matching steps
from the following list:
If foster parenting is enabled and target is a table, tbody, tfoot,
thead, or tr element
Foster parenting happens when content is misnested in tables.

Run these substeps:
1. Let last template be the last template element in the
  stack of open elements, if any.
2. Let last table be the last table element in the
  stack of open elements, if any.
3. If there is a last template and either there is no last table, or there is one, but last template is lower
  (more recently added) than last table in the stack of open
  elements, then: let adjusted insertion location be inside last template‘s template contents, after its last child (if any),
  and abort these steps.
4. If there is no last table, then let adjusted insertion location be inside the first element in the stack of open elements (the
  html element), after its last child (if any), and abort these steps.
  (fragment case)
5. If last table has a parent node, then let adjusted insertion location be inside last table‘s parent
  node, immediately before last table, and abort these steps.
6. Let previous element be the element immediately above last table in the stack of open elements.
7. Let adjusted insertion location be inside previous element, after its last child (if any).
These steps are involved in part because it’s possible for elements, the
table element in this case in particular, to have been moved by a script around
in the DOM, or indeed removed from the DOM entirely, after the element was inserted by the
parser.
Otherwise

Let adjusted insertion location be inside target,
after its last child (if any).
If the adjusted insertion location is inside a template
element, let it instead be inside the template element’s template
contents, after its last child (if any).
Return the adjusted insertion location.

When the steps below require the UA to create an
element for a token in a particular given namespace and with a
particular intended parent, the UA must run the following steps:

If the active speculative HTML parser is not null, then return the result of
creating a speculative mock element
given given namespace, the tag name of the given token, and the attributes of the
given token.
Otherwise, optionally create a speculative mock element given given namespace, the tag name of the given token, and the attributes of the given token.

The result is not used. This step allows for a speculative fetch to
be initiated from non-speculative parsing. The fetch is still speculative at this point,
because, for example, by the time the element is inserted, intended parent might
have been removed from the document.
Let document be intended parent‘s node document.
Let local name be the tag name of the token.
Let is be the value of the «is» attribute in the
given token, if such an attribute exists, or null otherwise.
Let definition be the result of looking up a custom element definition given document, given namespace, local name, and is.
If definition is non-null and the parser was not created as part of the
HTML fragment parsing algorithm, then let will execute script be true.
Otherwise, let it be false.
If will execute script is true, then:
1. Increment document‘s throw-on-dynamic-markup-insertion
  counter.
2. If the JavaScript execution context stack is empty, then perform a
  microtask checkpoint.
3. Push a new element queue onto document‘s relevant
  agent’s custom element reactions stack.
Let element be the result of creating an
element given document, localName, given namespace, null, and is. If will execute script is true, set the
synchronous custom elements flag; otherwise, leave it unset.

This will cause custom element
constructors to run, if will execute script is true. However, since we
incremented the throw-on-dynamic-markup-insertion counter, this cannot cause new characters to be inserted into the tokenizer, or the document to be blown away.
Append each attribute in the given
token to element.

This can enqueue a custom element callback reaction for the
attributeChangedCallback, which might run immediately (in the next
step).

Even though the is attribute governs the creation of a customized built-in element, it is
not present during the execution of the relevant custom element constructor; it is
appended in this step, along with all other attributes.
If will execute script is true, then:
1. Let queue be the result of popping from document‘s relevant
  agent’s custom element reactions stack. (This will be the same
  element queue as was pushed above.)
2. Invoke custom element reactions in queue.
3. Decrement document‘s throw-on-dynamic-markup-insertion
  counter.
If element has an xmlns attribute in the XMLNS
namespace whose value is not exactly the same as the element’s namespace, that is a
parse error. Similarly, if element has an xmlns:xlink attribute in the XMLNS namespace whose value is not the
XLink Namespace, that is a parse error.
If element is a resettable element, invoke
its reset algorithm. (This initializes the
element’s value and checkedness based on the element’s attributes.)
If element is a form-associated element and not a
form-associated custom element, the
form element pointer is not null, there is no
template element on the stack of open elements, element is
either not listed or doesn’t have a form attribute, and the intended parent is in the same
tree as the element pointed to by the form element
pointer, then associate element
with the form element pointed to by the form element
pointer and set element‘s parser inserted flag.
Return element.

When the steps below require the user agent to insert a foreign element for a token
in a given namespace, the user agent must run these steps:

Let the adjusted insertion location be the appropriate place for
inserting a node.
Let element be the result of creating an element for the token in the given namespace, with the intended
parent being the element in which the adjusted insertion location finds
itself.
If it is possible to insert element at the adjusted insertion location,
then:
1. If the parser was not created as part of the HTML fragment parsing
  algorithm, then push a new element queue onto element‘s
  relevant agent’s custom element reactions stack.
2. Insert element at the adjusted insertion location.
3. If the parser was not created as part of the HTML fragment parsing
  algorithm, then pop the element queue from element‘s
  relevant agent’s custom element reactions stack, and invoke
  custom element reactions in that queue.
If the adjusted insertion location cannot accept more
elements, e.g. because it’s a Document that already has an element child, then
element is dropped on the floor.
Push element onto the stack of open elements so that it is the new
current node.
Return element.

When the steps below require the user agent to insert an HTML element for a token,
the user agent must insert a foreign element for the token, in the HTML
namespace.

When the steps below require the user agent to adjust MathML attributes for a token,
then, if the token has an attribute named definitionurl, change its name to
definitionURL (note the case difference).

When the steps below require the user agent to adjust SVG attributes for a token,
then, for each attribute on the token whose attribute name is one of the ones in the first column
of the following table, change the attribute’s name to the name given in the corresponding cell in
the second column. (This fixes the case of SVG attributes that are not all lowercase.)

Attribute name on token	Attribute name on element
`attributename`	`attributeName`
`attributetype`	`attributeType`
`basefrequency`	`baseFrequency`
`baseprofile`	`baseProfile`
`calcmode`	`calcMode`
`clippathunits`	`clipPathUnits`
`diffuseconstant`	`diffuseConstant`
`edgemode`	`edgeMode`
`filterunits`	`filterUnits`
`glyphref`	`glyphRef`
`gradienttransform`	`gradientTransform`
`gradientunits`	`gradientUnits`
`kernelmatrix`	`kernelMatrix`
`kernelunitlength`	`kernelUnitLength`
`keypoints`	`keyPoints`
`keysplines`	`keySplines`
`keytimes`	`keyTimes`
`lengthadjust`	`lengthAdjust`
`limitingconeangle`	`limitingConeAngle`
`markerheight`	`markerHeight`
`markerunits`	`markerUnits`
`markerwidth`	`markerWidth`
`maskcontentunits`	`maskContentUnits`
`maskunits`	`maskUnits`
`numoctaves`	`numOctaves`
`pathlength`	`pathLength`
`patterncontentunits`	`patternContentUnits`
`patterntransform`	`patternTransform`
`patternunits`	`patternUnits`
`pointsatx`	`pointsAtX`
`pointsaty`	`pointsAtY`
`pointsatz`	`pointsAtZ`
`preservealpha`	`preserveAlpha`
`preserveaspectratio`	`preserveAspectRatio`
`primitiveunits`	`primitiveUnits`
`refx`	`refX`
`refy`	`refY`
`repeatcount`	`repeatCount`
`repeatdur`	`repeatDur`
`requiredextensions`	`requiredExtensions`
`requiredfeatures`	`requiredFeatures`
`specularconstant`	`specularConstant`
`specularexponent`	`specularExponent`
`spreadmethod`	`spreadMethod`
`startoffset`	`startOffset`
`stddeviation`	`stdDeviation`
`stitchtiles`	`stitchTiles`
`surfacescale`	`surfaceScale`
`systemlanguage`	`systemLanguage`
`tablevalues`	`tableValues`
`targetx`	`targetX`
`targety`	`targetY`
`textlength`	`textLength`
`viewbox`	`viewBox`
`viewtarget`	`viewTarget`
`xchannelselector`	`xChannelSelector`
`ychannelselector`	`yChannelSelector`
`zoomandpan`	`zoomAndPan`

When the steps below require the user agent to adjust foreign attributes for a
token, then, if any of the attributes on the token match the strings given in the first column of
the following table, let the attribute be a namespaced attribute, with the prefix being the string
given in the corresponding cell in the second column, the local name being the string given in the
corresponding cell in the third column, and the namespace being the namespace given in the
corresponding cell in the fourth column. (This fixes the use of namespaced attributes, in
particular lang attributes in the XML
namespace.)

Attribute name	Prefix	Local name	Namespace
`xlink:actuate`	`xlink`	`actuate`	XLink namespace
`xlink:arcrole`	`xlink`	`arcrole`	XLink namespace
`xlink:href`	`xlink`	`href`	XLink namespace
`xlink:role`	`xlink`	`role`	XLink namespace
`xlink:show`	`xlink`	`show`	XLink namespace
`xlink:title`	`xlink`	`title`	XLink namespace
`xlink:type`	`xlink`	`type`	XLink namespace
`xml:lang`	`xml`	`lang`	XML namespace
`xml:space`	`xml`	`space`	XML namespace
`xmlns`	(none)	`xmlns`	XMLNS namespace
`xmlns:xlink`	`xmlns`	`xlink`	XMLNS namespace

When the steps below require the user agent to insert a character while processing a
token, the user agent must run the following steps:

Let data be the characters passed to the algorithm, or, if no
characters were explicitly specified, the character of the character token being
processed.
Let the adjusted insertion location be the appropriate
place for inserting a node.
If the adjusted insertion location is in a Document node,
then return.

The DOM will not let Document nodes have Text node
children, so they are dropped on the floor.
If there is a Text node immediately before the adjusted insertion location, then append data to that Text node’s data.

Otherwise, create a new Text node whose data is data and
whose node document is the same as that of the
element in which the adjusted insertion location finds itself, and insert
the newly created node at the adjusted insertion location.

Here are some sample inputs to the parser and the corresponding number of Text
nodes that they result in, assuming a user agent that executes scripts.

Input	Number of `Text` nodes
`A<script> var script = document.getElementsByTagName('script')[0]; document.body.removeChild(script); </script>B`	One `Text` node in the document, containing «AB».
`A<script> var text = document.createTextNode('B'); document.body.appendChild(text); </script>C`	Three `Text` nodes; «A» before the script, the script’s contents, and «BC» after the script (the parser appends to the `Text` node created by the script).
`A<script> var text = document.getElementsByTagName('script')[0].firstChild; text.data = 'B'; document.body.appendChild(text); </script>C`	Two adjacent `Text` nodes in the document, containing «A» and «BC».
`A<table>B<tr>C</tr>D</table>`	One `Text` node before the table, containing «ABCD». (This is caused by foster parenting.)
`A<table><tr> B</tr> C</table>`	One `Text` node before the table, containing «A B C» (A-space-B-space-C). (This is caused by foster parenting.)
`A<table><tr> B</tr> </em>C</table>`	One `Text` node before the table, containing «A BC» (A-space-B-C), and one `Text` node inside the table (as a child of a `tbody`) with a single space character. (Space characters separated from non-space characters by non-character tokens are not affected by foster parenting, even if those other tokens then get ignored.)

When the steps below require the user agent to while processing a
comment token, optionally with an explicitly insertion position position, the
user agent must run the following steps:

Let data be the data given in the comment token being
processed.
If position was specified, then let the adjusted insertion location be position. Otherwise, let adjusted insertion location be the appropriate place for inserting a node.
Create a Comment node whose data attribute is set to
data and whose node document is
the same as that of the node in which the adjusted insertion location finds
itself.
Insert the newly created node at the adjusted insertion location.

DOM mutation events must not fire for changes caused by the UA
parsing the document. This includes the parsing of any content inserted using document.write() and document.writeln() calls. [UIEVENTS]

However, mutation observers do fire, as required by DOM
.

13.2.6.2 Parsing elements that contain only text

The generic raw text element parsing algorithm and the generic RCDATA element
parsing algorithm consist of the following steps. These algorithms are always invoked in
response to a start tag token.

Insert an HTML element for the token.
If the algorithm that was invoked is the generic raw text element parsing
algorithm, switch the tokenizer to the RAWTEXT state; otherwise the algorithm
invoked was the generic RCDATA element parsing algorithm, switch the tokenizer to
the RCDATA state.
Let the original insertion mode be the current insertion
mode.
Then, switch the insertion mode to «text».

13.2.6.3 Closing elements that have implied end tags

When the steps below require the UA to generate implied end tags, then, while the
current node is a dd element, a dt element, an
li element, an optgroup element, an option element, a
p element, an rb element, an rp element, an rt
element, or an rtc element, the UA must pop the current node off the
stack of open elements.

If a step requires the UA to generate implied end tags but lists an element to exclude from the
process, then the UA must perform the above steps as if that element was not in the above
list.

When the steps below require the UA to generate all implied end tags thoroughly,
then, while the current node is a caption element, a
colgroup element, a dd element, a dt element, an
li element, an optgroup element, an option element, a
p element, an rb element, an rp element, an rt
element, an rtc element, a tbody element, a td element, a
tfoot element, a th element, a thead element, or a
tr element, the UA must pop the current node off the
stack of open elements.

13.2.6.4 The rules for parsing tokens in HTML content

13.2.6.4.1 The «initial» insertion mode

A Document object has an associated parser cannot change the mode flag
(a boolean). It is initially false.

When the user agent is to apply the rules for the «initial» insertion mode, the user agent must handle the token as
follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Ignore the token.

A comment token

Insert a comment as the last child of the Document object.

A DOCTYPE token

If the DOCTYPE token’s name is not «html«, or the token’s public
identifier is not missing, or the token’s system identifier is neither missing nor
«about:legacy-compat«, then there is a parse error.

Append a DocumentType node to the Document node, with its name set to the name given in the DOCTYPE token, or the
empty string if the name was missing; its public
ID set to the public identifier given in the DOCTYPE token, or the empty string if the
public identifier was missing; and its system ID
set to the system identifier given in the DOCTYPE token, or the empty string if the system
identifier was missing.

This also ensures that the DocumentType node is returned as the
value of the doctype attribute of the
Document object.

Then, if the document is not an iframe
srcdoc document, and the parser cannot
change the mode flag is false, and the DOCTYPE token matches one of the conditions in the
following list, then set the Document to quirks mode:

The force-quirks flag is set to on.
The name is not «html«.
The public identifier is set to: «-//W3O//DTD W3 HTML Strict 3.0//EN//»
The public identifier is set to: «-/W3C/DTD HTML 4.0 Transitional/EN»
The public identifier is set to: «HTML»
The system identifier is set to: «http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd»
The public identifier starts with: «+//Silmaril//dtd html Pro v0r11 19970101//»
The public identifier starts with: «-//AS//DTD HTML 3.0 asWedit + extensions//»
The public identifier starts with: «-//AdvaSoft Ltd//DTD HTML 3.0 asWedit + extensions//»
The public identifier starts with: «-//IETF//DTD HTML 2.0 Level 1//»
The public identifier starts with: «-//IETF//DTD HTML 2.0 Level 2//»
The public identifier starts with: «-//IETF//DTD HTML 2.0 Strict Level 1//»
The public identifier starts with: «-//IETF//DTD HTML 2.0 Strict Level 2//»
The public identifier starts with: «-//IETF//DTD HTML 2.0 Strict//»
The public identifier starts with: «-//IETF//DTD HTML 2.0//»
The public identifier starts with: «-//IETF//DTD HTML 2.1E//»
The public identifier starts with: «-//IETF//DTD HTML 3.0//»
The public identifier starts with: «-//IETF//DTD HTML 3.2 Final//»
The public identifier starts with: «-//IETF//DTD HTML 3.2//»
The public identifier starts with: «-//IETF//DTD HTML 3//»
The public identifier starts with: «-//IETF//DTD HTML Level 0//»
The public identifier starts with: «-//IETF//DTD HTML Level 1//»
The public identifier starts with: «-//IETF//DTD HTML Level 2//»
The public identifier starts with: «-//IETF//DTD HTML Level 3//»
The public identifier starts with: «-//IETF//DTD HTML Strict Level 0//»
The public identifier starts with: «-//IETF//DTD HTML Strict Level 1//»
The public identifier starts with: «-//IETF//DTD HTML Strict Level 2//»
The public identifier starts with: «-//IETF//DTD HTML Strict Level 3//»
The public identifier starts with: «-//IETF//DTD HTML Strict//»
The public identifier starts with: «-//IETF//DTD HTML//»
The public identifier starts with: «-//Metrius//DTD Metrius Presentational//»
The public identifier starts with: «-//Microsoft//DTD Internet Explorer 2.0 HTML Strict//»
The public identifier starts with: «-//Microsoft//DTD Internet Explorer 2.0 HTML//»
The public identifier starts with: «-//Microsoft//DTD Internet Explorer 2.0 Tables//»
The public identifier starts with: «-//Microsoft//DTD Internet Explorer 3.0 HTML Strict//»
The public identifier starts with: «-//Microsoft//DTD Internet Explorer 3.0 HTML//»
The public identifier starts with: «-//Microsoft//DTD Internet Explorer 3.0 Tables//»
The public identifier starts with: «-//Netscape Comm. Corp.//DTD HTML//»
The public identifier starts with: «-//Netscape Comm. Corp.//DTD Strict HTML//»
The public identifier starts with: «-//O'Reilly and Associates//DTD HTML 2.0//»
The public identifier starts with: «-//O'Reilly and Associates//DTD HTML Extended 1.0//»
The public identifier starts with: «-//O'Reilly and Associates//DTD HTML Extended Relaxed 1.0//»
The public identifier starts with: «-//SQ//DTD HTML 2.0 HoTMetaL + extensions//»
The public identifier starts with: «-//SoftQuad Software//DTD HoTMetaL PRO 6.0::19990601::extensions to HTML 4.0//»
The public identifier starts with: «-//SoftQuad//DTD HoTMetaL PRO 4.0::19971010::extensions to HTML 4.0//»
The public identifier starts with: «-//Spyglass//DTD HTML 2.0 Extended//»
The public identifier starts with: «-//Sun Microsystems Corp.//DTD HotJava HTML//»
The public identifier starts with: «-//Sun Microsystems Corp.//DTD HotJava Strict HTML//»
The public identifier starts with: «-//W3C//DTD HTML 3 1995-03-24//»
The public identifier starts with: «-//W3C//DTD HTML 3.2 Draft//»
The public identifier starts with: «-//W3C//DTD HTML 3.2 Final//»
The public identifier starts with: «-//W3C//DTD HTML 3.2//»
The public identifier starts with: «-//W3C//DTD HTML 3.2S Draft//»
The public identifier starts with: «-//W3C//DTD HTML 4.0 Frameset//»
The public identifier starts with: «-//W3C//DTD HTML 4.0 Transitional//»
The public identifier starts with: «-//W3C//DTD HTML Experimental 19960712//»
The public identifier starts with: «-//W3C//DTD HTML Experimental 970421//»
The public identifier starts with: «-//W3C//DTD W3 HTML//»
The public identifier starts with: «-//W3O//DTD W3 HTML 3.0//»
The public identifier starts with: «-//WebTechs//DTD Mozilla HTML 2.0//»
The public identifier starts with: «-//WebTechs//DTD Mozilla HTML//»
The system identifier is missing and the public identifier starts with: «-//W3C//DTD HTML 4.01 Frameset//»
The system identifier is missing and the public identifier starts with: «-//W3C//DTD HTML 4.01 Transitional//»

Otherwise, if the document is not an iframe srcdoc document, and the parser cannot change
the mode flag is false, and the DOCTYPE token matches one of the conditions in the
following list, then then set the Document to limited-quirks mode:

The public identifier starts with: «-//W3C//DTD XHTML 1.0 Frameset//»
The public identifier starts with: «-//W3C//DTD XHTML 1.0 Transitional//»
The system identifier is not missing and the public identifier starts with: «-//W3C//DTD HTML 4.01 Frameset//»
The system identifier is not missing and the public identifier starts with: «-//W3C//DTD HTML 4.01 Transitional//»

The system identifier and public identifier strings must be compared to the values given in
the lists above in an ASCII case-insensitive manner. A system identifier whose
value is the empty string is not considered missing for the purposes of the conditions
above.

Then, switch the insertion mode to «before html».

Anything else

If the document is not an iframe srcdoc document, then this is a parse
error; if the parser cannot change the mode flag is false, set the
Document to quirks mode.

In any case, switch the insertion mode to «before html», then reprocess the token.

13.2.6.4.2 The «before html» insertion mode

When the user agent is to apply the rules for the «before html» insertion mode, the user agent must handle the token as
follows:

A DOCTYPE token

Parse error. Ignore the token.

A comment token

Insert a comment as the last child of the Document object.

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Ignore the token.

A start tag whose tag name is «html»

Create an element for the token in the HTML namespace, with the
Document as the intended parent. Append it to the Document object. Put
this element in the stack of open elements.

Switch the insertion mode to «before
head».

An end tag whose tag name is one of: «head», «body», «html», «br»

Act as described in the «anything else» entry below.

Any other end tag

Parse error. Ignore the token.

Anything else

Create an html element whose node document is the Document object. Append
it to the Document object. Put this element in the stack of open
elements.

Switch the insertion mode to «before
head», then reprocess the token.

The document element can end up being removed from the Document
object, e.g. by scripts; nothing in particular happens in such cases, content continues being
appended to the nodes as described in the next section.

13.2.6.4.3 The «before head» insertion mode

When the user agent is to apply the rules for the «before head» insertion mode, the user agent must handle the token as
follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Ignore the token.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is «head»

Insert an HTML element for the token.

Set the head element pointer to the newly created
head element.

Switch the insertion mode to «in
head».

An end tag whose tag name is one of: «head», «body», «html», «br»

Act as described in the «anything else» entry below.

Any other end tag

Parse error. Ignore the token.

Anything else

Insert an HTML element for a «head» start tag token with no attributes.

Set the head element pointer to the newly created
head element.

Switch the insertion mode to «in
head».

Reprocess the current token.

13.2.6.4.4 The «in head» insertion mode

When the user agent is to apply the rules for the «in
head» insertion mode, the user agent must handle the token as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Insert the character.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is one of: «base», «basefont», «bgsound», «link»

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

A start tag whose tag name is «meta»

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

If the active speculative HTML parser is null, then:

If the element has a charset attribute, and getting an encoding from
its value results in an encoding, and the
confidence is currently tentative,
then change the encoding to the resulting encoding.
Otherwise, if the element has an http-equiv
attribute whose value is an ASCII case-insensitive match for the string «Content-Type«, and the element has a content attribute, and applying the algorithm for
extracting a character encoding from a meta element to that attribute’s
value returns an encoding, and the
confidence is currently tentative,
then change the encoding to the extracted encoding.

The speculative HTML parser doesn’t speculatively apply character
encoding declarations in order to reduce implementation complexity.

A start tag whose tag name is «title»

Follow the generic RCDATA element parsing algorithm.

A start tag whose tag name is «noscript», if the scripting flag is enabled

A start tag whose tag name is one of: «noframes», «style»

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is «noscript», if the scripting flag is disabled

Insert an HTML element for the token.

Switch the insertion mode to «in
head noscript».

A start tag whose tag name is «script»

Run these steps:

Let the adjusted insertion location be the appropriate place
for inserting a node.
Create an element for the token in the HTML namespace, with
the intended parent being the element in which the adjusted insertion location finds itself.
Set the element’s parser document to the Document, and set the
element’s force async to false.

This ensures that, if the script is external, any document.write() calls in the script will execute in-line,
instead of blowing the document away, as would happen in most other cases. It also prevents
the script from executing until the end tag is seen.
If the parser was created as part of the HTML fragment parsing algorithm,
then set the script element’s already started to true.
(fragment case)
If the parser was invoked via the document.write() or document.writeln() methods, then optionally set the
script element’s already started to true. (For example, the user
agent might use this clause to prevent execution of cross-origin
scripts inserted via document.write() under slow
network conditions, or when the page has already taken a long time to load.)
Insert the newly created element at the adjusted insertion location.
Push the element onto the stack of open elements so that it is the new
current node.
Switch the tokenizer to the script data state.
Let the original insertion mode be the current insertion
mode.
Switch the insertion mode to «text».

An end tag whose tag name is «head»

Pop the current node (which will be the head element) off the
stack of open elements.

Switch the insertion mode to «after
head».

An end tag whose tag name is one of: «body», «html», «br»

Act as described in the «anything else» entry below.

A start tag whose tag name is «template»

Insert an HTML element for the token.

Insert a marker at the end of the list of
active formatting elements.

Set the frameset-ok flag to «not ok».

Switch the insertion mode to «in
template».

Push «in template» onto the stack of
template insertion modes so that it is the new current template insertion
mode.

An end tag whose tag name is «template»

If there is no template element on the stack of open elements, then
this is a parse error; ignore the token.

Otherwise, run these steps:

Generate all implied end tags thoroughly.
If the current node is not a template element, then this is a
parse error.
Pop elements from the stack of open elements until a template
element has been popped from the stack.
Clear the list of active formatting elements up to the last marker.
Pop the current template insertion mode off the stack of template
insertion modes.
Reset the insertion mode appropriately.

A start tag whose tag name is «head»

Any other end tag

Parse error. Ignore the token.

Anything else

Pop the current node (which will be the head element) off the
stack of open elements.

Switch the insertion mode to «after
head».

Reprocess the token.

13.2.6.4.5 The «in head noscript» insertion mode

When the user agent is to apply the rules for the «in head noscript» insertion mode, the user agent must handle the
token as follows:

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

An end tag whose tag name is «noscript»

Pop the current node (which will be a noscript element) from the
stack of open elements; the new current node will be a
head element.

Switch the insertion mode to «in
head».

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

A comment token

A start tag whose tag name is one of: «basefont», «bgsound», «link», «meta», «noframes», «style»

Process the token using the rules for the «in head» insertion mode.

An end tag whose tag name is «br»

Act as described in the «anything else» entry below.

A start tag whose tag name is one of: «head», «noscript»

Any other end tag

Parse error. Ignore the token.

Anything else

Parse error.

Pop the current node (which will be a noscript element) from the
stack of open elements; the new current node will be a
head element.

Switch the insertion mode to «in
head».

Reprocess the token.

13.2.6.4.6 The «after head» insertion mode

When the user agent is to apply the rules for the «after head» insertion mode, the user agent must handle the token as
follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Insert the character.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is «body»

Insert an HTML element for the token.

Set the frameset-ok flag to «not ok».

Switch the insertion mode to «in
body».

A start tag whose tag name is «frameset»

Insert an HTML element for the token.

Switch the insertion mode to «in
frameset».

A start tag whose tag name is one of: «base», «basefont», «bgsound», «link», «meta», «noframes», «script», «style», «template», «title»

Parse error.

Push the node pointed to by the head element pointer onto
the stack of open elements.

Process the token using the rules for the «in head» insertion mode.

Remove the node pointed to by the head element pointer
from the stack of open elements. (It might not be the current node at
this point.)

The head element pointer cannot be null at
this point.

An end tag whose tag name is «template»

Process the token using the rules for the «in head» insertion mode.

An end tag whose tag name is one of: «body», «html», «br»

Act as described in the «anything else» entry below.

A start tag whose tag name is «head»

Any other end tag

Parse error. Ignore the token.

Anything else

Insert an HTML element for a «body» start tag token with no attributes.

Switch the insertion mode to «in
body».

Reprocess the current token.

13.2.6.4.7 The «in body» insertion mode

When the user agent is to apply the rules for the «in
body» insertion mode, the user agent must handle the token as follows:

A character token that is U+0000 NULL

Parse error. Ignore the token.

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Reconstruct the active formatting elements, if any.

Insert the token’s character.

Any other character token

Reconstruct the active formatting elements, if any.

Insert the token’s character.

Set the frameset-ok flag to «not ok».

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Parse error.

If there is a template element on the stack of open elements, then
ignore the token.

Otherwise, for each attribute on the token, check to see if the attribute is already present
on the top element of the stack of open elements. If it is not, add the attribute
and its corresponding value to that element.

A start tag whose tag name is one of: «base», «basefont», «bgsound», «link», «meta», «noframes», «script», «style», «template», «title»

An end tag whose tag name is «template»

Process the token using the rules for the «in head» insertion mode.

A start tag whose tag name is «body»

Parse error.

If the second element on the stack of open elements is not a body
element, if the stack of open elements has only one node on it, or if there is a
template element on the stack of open elements, then ignore the token.
(fragment case)

Otherwise, set the frameset-ok flag to «not ok»; then, for each attribute on the
token, check to see if the attribute is already present on the body element (the
second element) on the stack of open elements, and if it is not, add the attribute
and its corresponding value to that element.

A start tag whose tag name is «frameset»

Parse error.

If the stack of open elements has only one node on it, or if the second element
on the stack of open elements is not a body element, then ignore the
token. (fragment case)

If the frameset-ok flag is set to «not ok», ignore the token.

Otherwise, run the following steps:

Remove the second element on the stack of open elements from its parent
node, if it has one.
Pop all the nodes from the bottom of the stack of open elements, from the
current node up to, but not including, the root html element.
Insert an HTML element for the token.
Switch the insertion mode to «in
frameset».

An end-of-file token

If the stack of template insertion modes is not empty, then process the token
using the rules for the «in
template» insertion mode.

Otherwise, follow these steps:

If there is a node in the stack of open elements that is not either a
dd element, a dt element, an li element, an
optgroup element, an option element, a p element, an
rb element, an rp element, an rt element, an
rtc element, a tbody element, a td element, a
tfoot element, a th element, a thead element, a
tr element, the body element, or the html element, then
this is a parse error.
Stop parsing.

An end tag whose tag name is «body»

If the stack of open elements does not have a body element in scope, this is a parse error;
ignore the token.

Otherwise, if there is a node in the stack of open elements that is not either a
dd element, a dt element, an li element, an
optgroup element, an option element, a p element, an
rb element, an rp element, an rt element, an
rtc element, a tbody element, a td element, a
tfoot element, a th element, a thead element, a
tr element, the body element, or the html element, then
this is a parse error.

Switch the insertion mode to «after
body».

An end tag whose tag name is «html»

If the stack of open elements does not have a body element in scope, this is a parse error;
ignore the token.

Switch the insertion mode to «after
body».

Reprocess the token.

A start tag whose tag name is one of: «address», «article», «aside», «blockquote», «center», «details», «dialog», «dir», «div», «dl», «fieldset», «figcaption», «figure», «footer», «header», «hgroup», «main», «menu», «nav», «ol», «p», «section», «summary», «ul»

If the stack of open elements has a
p element in button scope, then close a p
element.

Insert an HTML element for the token.

A start tag whose tag name is one of: «h1», «h2», «h3», «h4», «h5», «h6»

If the stack of open elements has a
p element in button scope, then close a p
element.

If the current node is an HTML element whose
tag name is one of «h1», «h2», «h3», «h4», «h5», or «h6», then this is a parse
error; pop the current node off the stack of open elements.

Insert an HTML element for the token.

A start tag whose tag name is one of: «pre», «listing»

If the stack of open elements has
a p element in button scope, then close a p
element.

Insert an HTML element for the token.

If the next token is a U+000A LINE FEED (LF) character token, then ignore that
token and move on to the next one. (Newlines at the start of pre blocks are ignored
as an authoring convenience.)

Set the frameset-ok flag to «not ok».

A start tag whose tag name is «form»

If the form element pointer is not null, and there is
no template element on the stack of open elements, then this is a
parse error; ignore the token.

Otherwise:

If the stack of open elements has
a p element in button scope, then close a p
element.

Insert an HTML element for the token, and, if there is no template
element on the stack of open elements, set the form element pointer to point to the element created.

A start tag whose tag name is «li»

Run these steps:

Set the frameset-ok flag to «not ok».
Initialize node to be the current
node (the bottommost node of the stack).
Loop: If node is an li element, then run these
substeps:
1. Generate implied end tags, except for li elements.
2. If the current node is not an li element, then this is a
  parse error.
3. Pop elements from the stack of open elements until an li
  element has been popped from the stack.
4. Jump to the step labeled done below.
If node is in the special category, but is not an
address, div, or p element, then jump to the step
labeled done below.
Otherwise, set node to the previous entry in the stack of open
elements and return to the step labeled loop.
Done: If the stack of open elements has a p element in button scope, then close a
p element.
Finally, insert an HTML element for the token.

A start tag whose tag name is one of: «dd», «dt»

Run these steps:

Set the frameset-ok flag to «not ok».
Initialize node to be the current
node (the bottommost node of the stack).
Loop: If node is a dd element, then run these
substeps:
1. Generate implied end tags, except for dd elements.
2. If the current node is not a dd element, then this is a
  parse error.
3. Pop elements from the stack of open elements until a dd
  element has been popped from the stack.
4. Jump to the step labeled done below.
If node is a dt element, then run these substeps:
1. Generate implied end tags, except for dt elements.
2. If the current node is not a dt element, then this is a
  parse error.
3. Pop elements from the stack of open elements until a dt
  element has been popped from the stack.
4. Jump to the step labeled done below.
If node is in the special category, but is not an
address, div, or p element, then jump to the step
labeled done below.
Otherwise, set node to the previous entry in the stack of open
elements and return to the step labeled loop.
Done: If the stack of open elements has a p element in button scope, then close a
p element.
Finally, insert an HTML element for the token.

A start tag whose tag name is «plaintext»

If the stack of open elements has a
p element in button scope, then close a p
element.

Insert an HTML element for the token.

Switch the tokenizer to the PLAINTEXT state.

Once a start tag with the tag name «plaintext» has been seen, that will be the
last token ever seen other than character tokens (and the end-of-file token), because there is
no way to switch out of the PLAINTEXT state.

A start tag whose tag name is «button»

If the stack of open elements has a
button element in scope, then run these substeps:
1. Parse error.
2. Generate implied end tags.
3. Pop elements from the stack of open elements until a button
  element has been popped from the stack.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token.
Set the frameset-ok flag to «not ok».

An end tag whose tag name is one of: «address», «article», «aside», «blockquote», «button», «center», «details», «dialog», «dir», «div», «dl», «fieldset», «figcaption», «figure», «footer», «header», «hgroup», «listing», «main», «menu», «nav», «ol», «pre», «section», «summary», «ul»

If the stack of open elements does not have an element in scope that is an HTML
element with the same tag name as that of the token, then this is a parse
error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not an HTML element with
the same tag name as that of the token, then this is a
parse error.
Pop elements from the stack of open elements until an HTML element with the same tag name as the token has been popped from the
stack.

An end tag whose tag name is «form»

If there is no template element on the stack of open elements, then
run these substeps:

Let node be the element that the form
element pointer is set to, or null if it is not set to an element.
Set the form element pointer to null.
If node is null or if the stack of open elements does
not have node in scope, then
this is a parse error; return and ignore the token.
Generate implied end tags.
If the current node is not node, then this is a
parse error.
Remove node from the stack of open elements.

If there is a template element on the stack of open
elements, then run these substeps instead:

If the stack of open elements does not have a form element in scope, then this is a parse
error; return and ignore the token.
Generate implied end tags.
If the current node is not a form element, then this is a
parse error.
Pop elements from the stack of open elements until a form
element has been popped from the stack.

An end tag whose tag name is «p»

If the stack of open elements does not have a p element in button scope, then this is a parse
error; insert an HTML element for a «p» start tag token with no
attributes.

Close a p element.

An end tag whose tag name is «li»

If the stack of open elements does not have an li element in list item scope, then this is a parse
error; ignore the token.

Otherwise, run these steps:

Generate implied end tags, except for li elements.
If the current node is not an li element, then this is a
parse error.
Pop elements from the stack of open elements until an li
element has been popped from the stack.

An end tag whose tag name is one of: «dd», «dt»

If the stack of open elements does not have an element in scope that is an HTML
element with the same tag name as that of the token, then this is a parse
error; ignore the token.

Otherwise, run these steps:

Generate implied end tags, except for HTML elements with the
same tag name as the token.
If the current node is not an HTML
element with the same tag name as that of the token, then this is a parse
error.
Pop elements from the stack of open elements until an HTML element with the same tag name as the token has been popped from the
stack.

An end tag whose tag name is one of: «h1», «h2», «h3», «h4», «h5», «h6»

If the stack of open elements does not have an element in scope that is an HTML
element and whose tag name is one of «h1», «h2», «h3», «h4», «h5», or «h6», then this is
a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not an HTML
element with the same tag name as that of the token, then this is a parse
error.
Pop elements from the stack of open elements until an HTML element whose tag name is one of «h1», «h2», «h3», «h4», «h5», or «h6»
has been popped from the stack.

An end tag whose tag name is «sarcasm»

Take a deep breath, then act as described in the «any other end
tag» entry below.

A start tag whose tag name is «a»

If the list of active formatting elements contains an a element
between the end of the list and the last marker on
the list (or the start of the list if there is no marker on the list), then this is a parse
error; run the adoption agency algorithm for the token, then remove that
element from the list of active formatting elements and the stack of open
elements if the adoption agency algorithm didn’t already remove it (it might
not have if the element is not in table
scope).

In the non-conforming stream
<a href="a">a<table><a href="b">b</table>x, the first
a element would be closed upon seeing the second one, and the «x» character would
be inside a link to «b», not to «a». This is despite the fact that the outer a
element is not in table scope (meaning that a regular </a> end tag at the start
of the table wouldn’t close the outer a element). The result is that the two
a elements are indirectly nested inside each other — non-conforming markup
will often result in non-conforming DOMs when parsed.

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Push onto the list of active
formatting elements that element.

A start tag whose tag name is one of: «b», «big», «code», «em», «font», «i», «s», «small», «strike», «strong», «tt», «u»

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Push onto the list of active
formatting elements that element.

A start tag whose tag name is «nobr»

Reconstruct the active formatting elements, if any.

If the stack of open elements has a
nobr element in scope, then this is a parse error; run the
adoption agency algorithm for the token, then once again reconstruct the
active formatting elements, if any.

Insert an HTML element for the token. Push onto the list of active
formatting elements that element.

An end tag whose tag name is one of: «a», «b», «big», «code», «em», «font», «i», «nobr», «s», «small», «strike», «strong», «tt», «u»

Run the adoption agency algorithm for the token.

A start tag whose tag name is one of: «applet», «marquee», «object»

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

Insert a marker at the end of the list of
active formatting elements.

Set the frameset-ok flag to «not ok».

An end tag token whose tag name is one of: «applet», «marquee», «object»

If the stack of open elements does not have an element in scope that is an HTML
element with the same tag name as that of the token, then this is a parse
error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not an HTML
element with the same tag name as that of the token, then this is a parse
error.
Pop elements from the stack of open elements until an HTML element with the same tag name as the token has been popped from the
stack.
Clear the list of active formatting elements up to the last marker.

A start tag whose tag name is «table»

If the Document is not set to quirks mode, and the
stack of open elements has a
p element in button scope, then close a p
element.

Insert an HTML element for the token.

Set the frameset-ok flag to «not ok».

Switch the insertion mode to «in
table».

An end tag whose tag name is «br»

Parse error. Drop the attributes from the token, and act as described in the
next entry; i.e. act as if this was a «br» start tag token with no attributes, rather than the
end tag token that it actually is.

A start tag whose tag name is one of: «area», «br», «embed», «img», «keygen», «wbr»

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

Set the frameset-ok flag to «not ok».

A start tag whose tag name is «input»

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

If the token does not have an attribute with the name «type», or if it does, but that
attribute’s value is not an ASCII case-insensitive match for the string «hidden«, then: set the frameset-ok flag to «not ok».

A start tag whose tag name is one of: «param», «source», «track»

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

A start tag whose tag name is «hr»

If the stack of open elements has a
p element in button scope, then close a p
element.

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

Set the frameset-ok flag to «not ok».

A start tag whose tag name is «image»

Parse error. Change the token’s tag name to «img» and reprocess it. (Don’t
ask.)

A start tag whose tag name is «textarea»

Run these steps:

Insert an HTML element for the token.
If the next token is a U+000A LINE FEED (LF) character token, then ignore
that token and move on to the next one. (Newlines at the start of textarea
elements are ignored as an authoring convenience.)
Switch the tokenizer to the RCDATA state.
Let the original insertion mode be the current insertion
mode.
Set the frameset-ok flag to «not ok».
Switch the insertion mode to «text».

A start tag whose tag name is «xmp»

If the stack of open elements has a
p element in button scope, then close a p
element.

Reconstruct the active formatting elements, if any.

Set the frameset-ok flag to «not ok».

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is «iframe»

Set the frameset-ok flag to «not ok».

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is «noembed»

A start tag whose tag name is «noscript», if the scripting flag is enabled

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is «select»

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

Set the frameset-ok flag to «not ok».

If the insertion mode is one of «in
table», «in caption», «in table body», «in row», or «in cell», then switch the
insertion mode to «in select in
table». Otherwise, switch the insertion mode to «in select».

A start tag whose tag name is one of: «optgroup», «option»

If the current node is an option element, then pop the
current node off the stack of open elements.

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

A start tag whose tag name is one of: «rb», «rtc»

If the stack of open elements has a
ruby element in scope, then generate implied end tags. If the
current node is not now a ruby element, this is a
parse error.

Insert an HTML element for the token.

A start tag whose tag name is one of: «rp», «rt»

If the stack of open elements has a
ruby element in scope, then generate implied end tags, except
for rtc elements. If the current node is not now a rtc
element or a ruby element, this is a parse error.

Insert an HTML element for the token.

A start tag whose tag name is «math»

Reconstruct the active formatting elements, if any.

Adjust MathML attributes for the token. (This fixes the case of MathML
attributes that are not all lowercase.)

Adjust foreign attributes for the token. (This fixes the use of namespaced
attributes, in particular XLink.)

Insert a foreign element for the token, in the MathML
namespace.

If the token has its self-closing flag set, pop the current node off the
stack of open elements and acknowledge
the token’s self-closing flag.

A start tag whose tag name is «svg»

Reconstruct the active formatting elements, if any.

Adjust SVG attributes for the token. (This fixes the case of SVG attributes that
are not all lowercase.)

Adjust foreign attributes for the token. (This fixes the use of namespaced
attributes, in particular XLink in SVG.)

Insert a foreign element for the token, in the SVG namespace.

If the token has its self-closing flag set, pop the current node off the
stack of open elements and acknowledge
the token’s self-closing flag.

A start tag whose tag name is one of: «caption», «col», «colgroup», «frame», «head», «tbody», «td», «tfoot», «th», «thead», «tr»

Parse error. Ignore the token.

Any other start tag

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

This element will be an ordinary
element.

Any other end tag

Run these steps:

Initialize node to be the current node (the bottommost
node of the stack).
Loop: If node is an HTML
element with the same tag name as the token, then:
1. Generate implied end tags, except for HTML elements with the
  same tag name as the token.
2. If node is not the current node, then this is a
  parse error.
3. Pop all the nodes from the current node up to node,
  including node, then stop these steps.
Otherwise, if node is in the special category, then
this is a parse error; ignore the token, and return.
Set node to the previous entry in the stack of open
elements.
Return to the step labeled loop.

When the steps above say the user agent is to close a p element, it
means that the user agent must run the following steps:

Generate implied end tags, except for p elements.
If the current node is not a p element, then this is a
parse error.
Pop elements from the stack of open elements until a p element
has been popped from the stack.

The adoption agency algorithm, which takes as its only argument
a token token for which the algorithm is being run, consists of the following
steps:

Let subject be token‘s tag name.
If the current node is an HTML element
whose tag name is subject, and the current node is not in the
list of active formatting elements, then pop the current node off the
stack of open elements and return.
Let outer loop counter be 0.
While true:
1. If outer loop counter is greater than or equal to 8, then return.
2. Increment outer loop counter by 1.
3. Let formatting element be the last element in the list of active
  formatting elements that:
  - is between the end of the list and the last marker in the list, if any, or the start of the list
    otherwise, and
  - has the tag name subject.
  If there is no such element, then return and instead act as described in the «any other end
  tag» entry above.
4. If formatting element is not in the stack of open elements, then
  this is a parse error; remove the element from the list, and return.
5. If formatting element is in the stack of open elements, but the
  element is not in scope, then this is a
  parse error; return.
6. If formatting element is not the current node, this is a
  parse error. (But do not return.)
7. Let furthest block be the topmost node in the stack of open
  elements that is lower in the stack than formatting element, and is an
  element in the special category. There might not be one.
8. If there is no furthest block, then the UA must first pop all the nodes from
  the bottom of the stack of open elements, from the current node up to
  and including formatting element, then remove formatting element from the
  list of active formatting elements, and finally return.
9. Let common ancestor be the element immediately above formatting element in the stack of open elements.
10. Let a bookmark note the position of formatting element in the list of
  active formatting elements relative to the elements on either side of it in the
  list.
11. Let node and last node be furthest block.
12. Let inner loop counter be 0.
13. While true:
  1. Increment inner loop counter by 1.
  2. Let node be the element immediately above node in the
    stack of open elements, or if node is no longer in the stack of
    open elements (e.g. because it got removed by this algorithm), the element that was immediately above node in
    the stack of open elements before node was removed.
  3. If node is formatting element, then break.
  4. If inner loop counter is greater than 3 and node is in the
    list of active formatting elements, then remove node from the
    list of active formatting elements.
  5. If node is not in the list of active
    formatting elements, then remove node from the stack of open
    elements and continue.
  6. Create an element for the token for which the element node was
    created, in the HTML namespace, with common ancestor as the intended
    parent; replace the entry for node in the list of active formatting
    elements with an entry for the new element, replace the entry for node in
    the stack of open elements with an entry for the new element, and let
    node be the new element.
  7. If last node is furthest block, then move the aforementioned
    bookmark to be immediately after the new node in the list of active
    formatting elements.
  8. Append last node to
    node.
  9. Set last node to node.
14. Insert whatever last node ended up being in the previous step at the
  appropriate place for inserting a node, but using common ancestor as the override target.
15. Create an element for the token for which formatting element was created, in the HTML namespace, with furthest block as the intended parent.
16. Take all of the child nodes of furthest block and append them to the
  element created in the last step.
17. Append that new element to furthest block.
18. Remove formatting element from the list of active formatting
  elements, and insert the new element into the list of active formatting
  elements at the position of the aforementioned bookmark.
19. Remove formatting element from the stack of open
  elements, and insert the new element into the stack of open elements
  immediately below the position of furthest block in that stack.

This algorithm’s name, the «adoption agency algorithm», comes from the way it
causes elements to change parents, and is in contrast with other possible algorithms for dealing
with misnested content.

13.2.6.4.8 The «text» insertion mode

When the user agent is to apply the rules for the «text» insertion mode, the user agent must handle the token as
follows:

A character token

Insert the token’s character.

This can never be a U+0000 NULL character; the tokenizer converts those to
U+FFFD REPLACEMENT CHARACTER characters.

An end-of-file token

Parse error.

If the current node is a script element, then set its already
started to true.

Pop the current node off the stack of open elements.

Switch the insertion mode to the original insertion mode and
reprocess the token.

An end tag whose tag name is «script»

If the active speculative HTML parser is null and the JavaScript execution
context stack is empty, then perform a microtask checkpoint.

Let script be the current node (which will be a
script element).

Pop the current node off the stack of open elements.

Switch the insertion mode to the original insertion mode.

Let the old insertion point have the same value as the current
insertion point. Let the insertion point be just before the next
input character.

Increment the parser’s script nesting level by one.

If the active speculative HTML parser is null, then prepare the script
element script. This might cause some script to execute, which might cause
new characters to be inserted into the tokenizer, and
might cause the tokenizer to output more tokens, resulting in a reentrant invocation of the parser.

Decrement the parser’s script nesting level by one. If the parser’s script
nesting level is zero, then set the parser pause flag to false.

Let the insertion point have the value of the old insertion point. (In other words, restore the insertion point to its previous value.
This value might be the «undefined» value.)

At this stage, if the pending parsing-blocking
script is not null, then:

If the script nesting level is not zero:

Set the parser pause flag to true, and abort the processing of any nested
invocations of the tokenizer, yielding control back to the caller. (Tokenization will resume
when the caller returns to the «outer» tree construction stage.)

The tree construction stage of this particular parser is being called reentrantly, say from a call to document.write().

Otherwise:

While the pending parsing-blocking script is not null:

Let the script be the pending parsing-blocking
script.
Set the pending parsing-blocking script to null.
Start the speculative HTML parser for this instance of the HTML
parser.
Block the tokenizer for this instance of the
HTML parser, such that the event loop will not run tasks that invoke the tokenizer.
If the parser’s Document has a style sheet that is blocking
scripts or the script‘s ready to be parser-executed is false:
spin the event loop until the parser’s Document has no style
sheet that is blocking scripts and the script‘s ready to be
parser-executed becomes true.
If this parser has been aborted in the meantime,
return.

This could happen if, e.g., while the spin the event loop
algorithm is running, the Document gets destroyed, or the document.open()
method gets invoked on the Document.
Stop the speculative HTML parser for this instance of the HTML
parser.
Unblock the tokenizer for this instance of the
HTML parser, such that tasks that invoke the
tokenizer can again be run.
Let the insertion point be just before the next input
character.
Increment the parser’s script nesting level by one (it should be zero
before this step, so this sets it to one).
Execute the script element the script.
Decrement the parser’s script nesting level by one. If the parser’s
script nesting level is zero (which it always should be at this point), then set
the parser pause flag to false.
Let the insertion point be undefined again.

Any other end tag

Pop the current node off the stack of open elements.

Switch the insertion mode to the original insertion mode.

13.2.6.4.9 The «in table» insertion mode

When the user agent is to apply the rules for the «in
table» insertion mode, the user agent must handle the token as follows:

A character token, if the current node is table, tbody, template, tfoot, thead, or tr element

Let the pending table character tokens be an empty list of tokens.

Let the original insertion mode be the current insertion mode.

Switch the insertion mode to «in
table text» and reprocess the token.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «caption»

Clear the stack back to a table context. (See below.)

Insert a marker at the end of the list of
active formatting elements.

Insert an HTML element for the token, then switch the insertion
mode to «in caption».

A start tag whose tag name is «colgroup»

Clear the stack back to a table context. (See below.)

Insert an HTML element for the token, then switch the insertion
mode to «in column group».

A start tag whose tag name is «col»

Clear the stack back to a table context. (See below.)

Insert an HTML element for a «colgroup» start tag token with no attributes, then
switch the insertion mode to «in
column group».

Reprocess the current token.

A start tag whose tag name is one of: «tbody», «tfoot», «thead»

Clear the stack back to a table context. (See below.)

Insert an HTML element for the token, then switch the insertion
mode to «in table body».

A start tag whose tag name is one of: «td», «th», «tr»

Clear the stack back to a table context. (See below.)

Insert an HTML element for a «tbody» start tag token with no attributes, then
switch the insertion mode to «in table
body».

Reprocess the current token.

A start tag whose tag name is «table»

Parse error.

If the stack of open elements does not have a table element in table scope, ignore the token.

Otherwise:

Pop elements from this stack until a table element has been popped from the
stack.

Reset the insertion mode appropriately.

Reprocess the token.

An end tag whose tag name is «table»

If the stack of open elements does not have a table element in table scope, this is a parse
error; ignore the token.

Otherwise:

Pop elements from this stack until a table element has been popped from the
stack.

Reset the insertion mode appropriately.

An end tag whose tag name is one of: «body», «caption», «col», «colgroup», «html», «tbody», «td», «tfoot», «th», «thead», «tr»

Parse error. Ignore the token.

A start tag whose tag name is one of: «style», «script», «template»

An end tag whose tag name is «template»

Process the token using the rules for the «in head» insertion
mode.

A start tag whose tag name is «input»

If the token does not have an attribute with the name «type», or if it does, but that
attribute’s value is not an ASCII case-insensitive match for the string «hidden«, then: act as described in the «anything else» entry below.

Otherwise:

Parse error.

Insert an HTML element for the token.

Pop that input element off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

A start tag whose tag name is «form»

Parse error.

If there is a template element on the stack of open elements, or if
the form element pointer is not null, ignore the
token.

Otherwise:

Insert an HTML element for the token, and set the form element pointer to point to the element created.

Pop that form element off the stack of open elements.

An end-of-file token

Process the token using the rules for the «in body» insertion mode.

Anything else

Parse error. Enable foster parenting, process
the token using the rules for the «in
body» insertion mode, and then disable foster
parenting.

When the steps above require the UA to clear the stack back to a table context, it
means that the UA must, while the current node is not a table,
template, or html element, pop elements from the stack of open
elements.

This is the same list of elements as used in the has an element in table scope steps.

The current node being an html element after this
process is a fragment case.

13.2.6.4.10 The «in table text» insertion mode

When the user agent is to apply the rules for the «in table text» insertion mode, the user agent must handle the token as
follows:

A character token that is U+0000 NULL

Parse error. Ignore the token.

Any other character token

Append the character token to the pending table character tokens list.

Anything else

If any of the tokens in the pending table character tokens list are character tokens that are not ASCII whitespace,
then this is a parse error: reprocess the character tokens in the pending table character tokens list using the
rules given in the «anything else» entry in the «in
table» insertion mode.

Otherwise, insert the characters given by the pending table character tokens list.

Switch the insertion mode to the original insertion mode and
reprocess the token.

13.2.6.4.11 The «in caption» insertion mode

When the user agent is to apply the rules for the «in
caption» insertion mode, the user agent must handle the token as follows:

An end tag whose tag name is «caption»

If the stack of open elements does not have a caption element in table scope, this is a parse
error; ignore the token. (fragment case)

Otherwise:

Generate implied end tags.

Now, if the current node is not a caption element, then this is a
parse error.

Pop elements from this stack until a caption element has been popped from the
stack.

Clear the list of active formatting elements up to the last marker.

Switch the insertion mode to «in
table».

A start tag whose tag name is one of: «caption», «col», «colgroup», «tbody», «td», «tfoot», «th», «thead», «tr»

An end tag whose tag name is «table»

If the stack of open elements does not have a caption element in table scope, this is a parse
error; ignore the token. (fragment case)

Otherwise:

Generate implied end tags.

Now, if the current node is not a caption element, then this is a
parse error.

Pop elements from this stack until a caption element has been popped from the
stack.

Clear the list of active formatting elements up to the last marker.

Switch the insertion mode to «in
table».

Reprocess the token.

An end tag whose tag name is one of: «body», «col», «colgroup», «html», «tbody», «td», «tfoot», «th», «thead», «tr»

Parse error. Ignore the token.

Anything else

Process the token using the rules for the «in body» insertion mode.

13.2.6.4.12 The «in column group» insertion mode

When the user agent is to apply the rules for the «in column group» insertion mode, the user agent must handle the token
as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Insert the character.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is «col»

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

An end tag whose tag name is «colgroup»

If the current node is not a colgroup element, then this is a
parse error; ignore the token.

Otherwise, pop the current node from the stack of open elements.
Switch the insertion mode to «in
table».

An end tag whose tag name is «col»

Parse error. Ignore the token.

A start tag whose tag name is «template»

An end tag whose tag name is «template»

Process the token using the rules for the «in head» insertion mode.

An end-of-file token

Process the token using the rules for the «in body» insertion mode.

Anything else

If the current node is not a colgroup element, then this is a
parse error; ignore the token.

Otherwise, pop the current node from the stack of open
elements.

Switch the insertion mode to «in
table».

Reprocess the token.

13.2.6.4.13 The «in table body» insertion mode

When the user agent is to apply the rules for the «in table body» insertion mode, the user agent must handle the token as
follows:

A start tag whose tag name is «tr»

Clear the stack back to a table body context. (See below.)

Insert an HTML element for the token, then switch the insertion
mode to «in row».

A start tag whose tag name is one of: «th», «td»

Parse error.

Clear the stack back to a table body context. (See below.)

Insert an HTML element for a «tr» start tag token with no attributes, then
switch the insertion mode to «in
row».

Reprocess the current token.

An end tag whose tag name is one of: «tbody», «tfoot», «thead»

If the stack of open elements does not have an element in table scope that is an HTML
element with the same tag name as the token, this is a parse error;
ignore the token.

Otherwise:

Clear the stack back to a table body context. (See below.)

Pop the current node from the stack of open elements. Switch the
insertion mode to «in table».

A start tag whose tag name is one of: «caption», «col», «colgroup», «tbody», «tfoot», «thead»

An end tag whose tag name is «table»

If the stack of open elements does not have a tbody, thead, or tfoot element in table
scope, this is a parse error; ignore the token.

Otherwise:

Clear the stack back to a table body context. (See below.)

Pop the current node from the stack of open elements. Switch the
insertion mode to «in table».

Reprocess the token.

An end tag whose tag name is one of: «body», «caption», «col», «colgroup», «html», «td», «th», «tr»

Parse error. Ignore the token.

Anything else

Process the token using the rules for the «in table» insertion mode.

When the steps above require the UA to clear the stack back to a table body context,
it means that the UA must, while the current node is not a tbody,
tfoot, thead, template, or html element, pop
elements from the stack of open elements.

The current node being an html element after this
process is a fragment case.

13.2.6.4.14 The «in row» insertion mode

When the user agent is to apply the rules for the «in
row» insertion mode, the user agent must handle the token as follows:

A start tag whose tag name is one of: «th», «td»

Clear the stack back to a table row context. (See below.)

Insert an HTML element for the token, then switch the insertion
mode to «in cell».

Insert a marker at the end of the list of
active formatting elements.

An end tag whose tag name is «tr»

If the stack of open elements does not have a tr element in table scope, this is a parse error;
ignore the token.

Otherwise:

Clear the stack back to a table row context. (See below.)

Pop the current node (which will be a tr element) from the
stack of open elements. Switch the insertion mode to «in table body».

A start tag whose tag name is one of: «caption», «col», «colgroup», «tbody», «tfoot», «thead», «tr»

An end tag whose tag name is «table»

If the stack of open elements does not have a tr element in table scope, this is a parse error;
ignore the token.

Otherwise:

Clear the stack back to a table row context. (See below.)

Pop the current node (which will be a tr element) from the
stack of open elements. Switch the insertion mode to «in table body».

Reprocess the token.

An end tag whose tag name is one of: «tbody», «tfoot», «thead»

If the stack of open elements does not have an element in table scope that is an HTML
element with the same tag name as the token, this is a parse error;
ignore the token.

If the stack of open elements does not have a tr element in table scope, ignore the token.

Otherwise:

Clear the stack back to a table row context. (See below.)

Pop the current node (which will be a tr element) from the
stack of open elements. Switch the insertion mode to «in table body».

Reprocess the token.

An end tag whose tag name is one of: «body», «caption», «col», «colgroup», «html», «td», «th»

Parse error. Ignore the token.

Anything else

Process the token using the rules for the «in table» insertion mode.

When the steps above require the UA to clear the stack back to a table row context,
it means that the UA must, while the current node is not a tr,
template, or html element, pop elements from the stack of open
elements.

The current node being an html element after this
process is a fragment case.

13.2.6.4.15 The «in cell» insertion mode

When the user agent is to apply the rules for the «in cell» insertion mode, the user agent must handle the token as follows:

An end tag whose tag name is one of: «td», «th»

If the stack of open elements does not have an element in table scope that is an HTML
element with the same tag name as that of the token, then this is a parse
error; ignore the token.

Otherwise:

Generate implied end tags.

Now, if the current node is not an HTML
element with the same tag name as the token, then this is a parse error.

Pop elements from the stack of open elements stack until an HTML element with the same tag name as the token has been popped from the
stack.

Clear the list of active formatting elements up to the last marker.

Switch the insertion mode to «in
row».

A start tag whose tag name is one of: «caption», «col», «colgroup», «tbody», «td», «tfoot», «th», «thead», «tr»

If the stack of open elements does not have a td or th element in table scope, then this
is a parse error; ignore the token. (fragment case)

Otherwise, close the cell (see below) and reprocess the token.

An end tag whose tag name is one of: «body», «caption», «col», «colgroup», «html»

Parse error. Ignore the token.

An end tag whose tag name is one of: «table», «tbody», «tfoot», «thead», «tr»

If the stack of open elements does not have an element in table scope that is an HTML
element with the same tag name as that of the token, then this is a parse
error; ignore the token.

Otherwise, close the cell (see below) and reprocess the token.

Anything else

Process the token using the rules for the «in body» insertion mode.

Where the steps above say to close the cell, they mean to run the following
algorithm:

Generate implied end tags.
If the current node is not now a td element or a th
element, then this is a parse error.
Pop elements from the stack of open elements stack until a td
element or a th element has been popped from the stack.
Clear the list of active formatting elements up to the last marker.
Switch the insertion mode to «in
row».

The stack of open elements cannot have both a td and a
th element in table scope at the
same time, nor can it have neither when the close the cell algorithm is invoked.

13.2.6.4.16 The «in select» insertion mode

When the user agent is to apply the rules for the «in
select» insertion mode, the user agent must handle the token as follows:

A character token that is U+0000 NULL

Parse error. Ignore the token.

Any other character token

Insert the token’s character.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is «option»

If the current node is an option element, pop that node from the
stack of open elements.

Insert an HTML element for the token.

A start tag whose tag name is «optgroup»

If the current node is an option element, pop that node from the
stack of open elements.

If the current node is an optgroup element, pop that node from the
stack of open elements.

Insert an HTML element for the token.

An end tag whose tag name is «optgroup»

First, if the current node is an option element, and the node
immediately before it in the stack of open elements is an optgroup
element, then pop the current node from the stack of open
elements.

If the current node is an optgroup element, then pop that node from
the stack of open elements. Otherwise, this is a parse error; ignore
the token.

An end tag whose tag name is «option»

If the current node is an option element, then pop that node from
the stack of open elements. Otherwise, this is a parse error; ignore
the token.

An end tag whose tag name is «select»

If the stack of open elements does not have a select element in select scope, this is a parse
error; ignore the token. (fragment case)

Otherwise:

Pop elements from the stack of open elements until a select element
has been popped from the stack.

Reset the insertion mode appropriately.

A start tag whose tag name is «select»

Parse error.

If the stack of open elements does not have a select element in select scope, ignore the token.
(fragment case)

Otherwise:

Pop elements from the stack of open elements until a select element
has been popped from the stack.

Reset the insertion mode appropriately.

It just gets treated like an end tag.

A start tag whose tag name is one of: «input», «keygen», «textarea»

Parse error.

If the stack of open elements does not have a select element in select scope, ignore the token.
(fragment case)

Otherwise:

Pop elements from the stack of open elements until a select element
has been popped from the stack.

Reset the insertion mode appropriately.

Reprocess the token.

A start tag whose tag name is one of: «script», «template»

An end tag whose tag name is «template»

Process the token using the rules for the «in head» insertion mode.

An end-of-file token

Process the token using the rules for the «in body» insertion mode.

Anything else

Parse error. Ignore the token.

13.2.6.4.17 The «in select in table» insertion mode

When the user agent is to apply the rules for the «in select in table» insertion mode, the user agent must handle the
token as follows:

A start tag whose tag name is one of: «caption», «table», «tbody», «tfoot», «thead», «tr», «td», «th»

Parse error.

Pop elements from the stack of open elements until a select element
has been popped from the stack.

Reset the insertion mode appropriately.

Reprocess the token.

An end tag whose tag name is one of: «caption», «table», «tbody», «tfoot», «thead», «tr», «td», «th»

Parse error.

If the stack of open elements does not have an element in table scope that is an HTML
element with the same tag name as that of the token, then ignore the token.

Otherwise:

Pop elements from the stack of open elements until a select element
has been popped from the stack.

Reset the insertion mode appropriately.

Reprocess the token.

Anything else

Process the token using the rules for the «in select» insertion mode.

13.2.6.4.18 The «in template» insertion mode

When the user agent is to apply the rules for the «in
template» insertion mode, the user agent must handle the token as follows:

A character token

A comment token

A DOCTYPE token

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is one of: «base», «basefont», «bgsound», «link», «meta», «noframes», «script», «style», «template», «title»

An end tag whose tag name is «template»

Process the token using the rules for the «in head» insertion mode.

A start tag whose tag name is one of: «caption», «colgroup», «tbody», «tfoot», «thead»

Pop the current template insertion mode off the stack of template
insertion modes.

Push «in table» onto the stack of
template insertion modes so that it is the new current template insertion
mode.

Switch the insertion mode to «in
table», and reprocess the token.

A start tag whose tag name is «col»

Pop the current template insertion mode off the stack of template
insertion modes.

Push «in column group» onto the
stack of template insertion modes so that it is the new current template
insertion mode.

Switch the insertion mode to «in
column group», and reprocess the token.

A start tag whose tag name is «tr»

Pop the current template insertion mode off the stack of template
insertion modes.

Push «in table body» onto the stack
of template insertion modes so that it is the new current template insertion
mode.

Switch the insertion mode to «in
table body», and reprocess the token.

A start tag whose tag name is one of: «td», «th»

Pop the current template insertion mode off the stack of template
insertion modes.

Push «in row» onto the stack of template
insertion modes so that it is the new current template insertion mode.

Switch the insertion mode to «in
row», and reprocess the token.

Any other start tag

Pop the current template insertion mode off the stack of template
insertion modes.

Push «in body» onto the stack of template
insertion modes so that it is the new current template insertion mode.

Switch the insertion mode to «in
body», and reprocess the token.

Any other end tag

Parse error. Ignore the token.

An end-of-file token

If there is no template element on the stack of open elements, then
stop parsing. (fragment case)

Otherwise, this is a parse error.

Pop elements from the stack of open elements until a template
element has been popped from the stack.

Clear the list of active formatting elements up to the last marker.

Pop the current template insertion mode off the stack of template
insertion modes.

Reset the insertion mode appropriately.

Reprocess the token.

13.2.6.4.19 The «after body» insertion mode

When the user agent is to apply the rules for the «after body» insertion mode, the user agent must handle the token as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Process the token using the rules for the «in body» insertion mode.

A comment token

Insert a comment as the last child of the first element in the stack of
open elements (the html element).

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

An end tag whose tag name is «html»

If the parser was created as part of the HTML fragment parsing algorithm, this
is a parse error; ignore the token. (fragment case)

Otherwise, switch the insertion mode to «after after body».

An end-of-file token

Stop parsing.

Anything else

Parse error. Switch the insertion mode to «in body» and reprocess the token.

13.2.6.4.20 The «in frameset» insertion mode

When the user agent is to apply the rules for the «in
frameset» insertion mode, the user agent must handle the token as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Insert the character.

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is «html»

Process the token using the rules for the «in body» insertion mode.

A start tag whose tag name is «frameset»

Insert an HTML element for the token.

An end tag whose tag name is «frameset»

If the current node is the root html element, then this is a
parse error; ignore the token. (fragment case)

Otherwise, pop the current node from the stack of open
elements.

If the parser was not created as part of the HTML fragment parsing algorithm
(fragment case), and the current node is no longer a
frameset element, then switch the insertion mode to «after frameset».

A start tag whose tag name is «frame»

Insert an HTML element for the token. Immediately pop the current
node off the stack of open elements.

Acknowledge the token’s self-closing
flag, if it is set.

A start tag whose tag name is «noframes»

Process the token using the rules for the «in head» insertion mode.

An end-of-file token

If the current node is not the root html element, then this is a
parse error.

The current node can only be the root
html element in the fragment case.

Stop parsing.

Anything else

Parse error. Ignore the token.

13.2.6.4.21 The «after frameset» insertion mode

When the user agent is to apply the rules for the «after frameset» insertion mode, the user agent must handle the token
as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE: Insert the character.
A comment token: Insert a comment.
A DOCTYPE token: Parse error. Ignore the token.
A start tag whose tag name is «html»: Process the token using the rules for the «in body» insertion mode.
An end tag whose tag name is «html»: Switch the insertion mode to «after after frameset».
A start tag whose tag name is «noframes»: Process the token using the rules for the «in head» insertion mode.
An end-of-file token: Stop parsing.
Anything else: Parse error. Ignore the token.

13.2.6.4.22 The «after after body» insertion mode

When the user agent is to apply the rules for the «after after body» insertion mode, the user agent must handle the token
as follows:

A comment token: Insert a comment as the last child of the Document object.
A DOCTYPE token
A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
A start tag whose tag name is «html»: Process the token using the rules for the «in body» insertion mode.
An end-of-file token: Stop parsing.
Anything else: Parse error. Switch the insertion mode to «in body» and reprocess the token.

13.2.6.4.23 The «after after frameset» insertion mode

When the user agent is to apply the rules for the «after after frameset» insertion mode, the user agent must handle the
token as follows:

A comment token: Insert a comment as the last child of the Document object.
A DOCTYPE token
A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
A start tag whose tag name is «html»: Process the token using the rules for the «in body» insertion mode.
An end-of-file token: Stop parsing.
A start tag whose tag name is «noframes»: Process the token using the rules for the «in head» insertion mode.
Anything else: Parse error. Ignore the token.

13.2.6.5 The rules for parsing tokens in foreign content

When the user agent is to apply the rules for parsing tokens in foreign content, the user agent
must handle the token as follows:

A character token that is U+0000 NULL

Parse error. Insert a U+FFFD REPLACEMENT
CHARACTER character.

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE

Insert the token’s character.

Any other character token

Insert the token’s character.

Set the frameset-ok flag to «not ok».

A comment token

Insert a comment.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is one of: «b», «big», «blockquote», «body», «br», «center», «code», «dd», «div», «dl», «dt», «em», «embed», «h1», «h2», «h3», «h4», «h5», «h6», «head», «hr», «i», «img», «li», «listing», «menu», «meta», «nobr», «ol», «p», «pre», «ruby», «s», «small», «span», «strong», «strike», «sub», «sup», «table», «tt», «u», «ul», «var»

A start tag whose tag name is «font», if the token has any attributes named «color», «face», or «size»

An end tag whose tag name is «br», «p»

Parse error.

While the current node is not a MathML text integration point, an
HTML integration point, or an element in the HTML namespace, pop
elements from the stack of open elements.

Reprocess the token according to the rules given in the section corresponding to the current
insertion mode in HTML content.

Any other start tag

If the adjusted current node is an element in the MathML namespace,
adjust MathML attributes for the token. (This fixes the case of MathML attributes
that are not all lowercase.)

If the adjusted current node is an element in the SVG namespace, and the
token’s tag name is one of the ones in the first column of the following table, change the tag
name to the name given in the corresponding cell in the second column. (This fixes the case of
SVG elements that are not all lowercase.)

Tag name	Element name
`altglyph`	`altGlyph`
`altglyphdef`	`altGlyphDef`
`altglyphitem`	`altGlyphItem`
`animatecolor`	`animateColor`
`animatemotion`	`animateMotion`
`animatetransform`	`animateTransform`
`clippath`	`clipPath`
`feblend`	`feBlend`
`fecolormatrix`	`feColorMatrix`
`fecomponenttransfer`	`feComponentTransfer`
`fecomposite`	`feComposite`
`feconvolvematrix`	`feConvolveMatrix`
`fediffuselighting`	`feDiffuseLighting`
`fedisplacementmap`	`feDisplacementMap`
`fedistantlight`	`feDistantLight`
`fedropshadow`	`feDropShadow`
`feflood`	`feFlood`
`fefunca`	`feFuncA`
`fefuncb`	`feFuncB`
`fefuncg`	`feFuncG`
`fefuncr`	`feFuncR`
`fegaussianblur`	`feGaussianBlur`
`feimage`	`feImage`
`femerge`	`feMerge`
`femergenode`	`feMergeNode`
`femorphology`	`feMorphology`
`feoffset`	`feOffset`
`fepointlight`	`fePointLight`
`fespecularlighting`	`feSpecularLighting`
`fespotlight`	`feSpotLight`
`fetile`	`feTile`
`feturbulence`	`feTurbulence`
`foreignobject`	`foreignObject`
`glyphref`	`glyphRef`
`lineargradient`	`linearGradient`
`radialgradient`	`radialGradient`
`textpath`	`textPath`

If the adjusted current node is an element in the SVG namespace,
adjust SVG attributes for the token. (This fixes the case of SVG attributes that
are not all lowercase.)

Adjust foreign attributes for the token. (This fixes the use of namespaced
attributes, in particular XLink in SVG.)

Insert a foreign element for the token, in the same namespace as the
adjusted current node.

If the token has its self-closing flag set, then run the appropriate steps from the
following list:

If the token’s tag name is «script», and the new current node is in the SVG namespace: Acknowledge the token’s self-closing
flag, and then act as described in the steps for a «script» end tag below.
Otherwise: Pop the current node off the stack of open elements and acknowledge the token’s self-closing
flag.

An end tag whose tag name is «script», if the current node is an SVG script element

Pop the current node off the stack of open elements.

Let the old insertion point have the same value as the current
insertion point. Let the insertion point be just before the next
input character.

Increment the parser’s script nesting level by one. Set the parser pause
flag to true.

If the active speculative HTML parser is null and the user agent supports SVG,
then Process the
SVG script element according to the SVG rules. [SVG]

Even if this causes new characters to be
inserted into the tokenizer, the parser will not be executed reentrantly, since the
parser pause flag is true.

Decrement the parser’s script nesting level by one. If the parser’s script
nesting level is zero, then set the parser pause flag to false.

Let the insertion point have the value of the old insertion point. (In other words, restore the insertion point to its previous value.
This value might be the «undefined» value.)

Any other end tag

Run these steps:

Initialize node to be the current node (the bottommost
node of the stack).
If node‘s tag name, converted to ASCII lowercase, is
not the same as the tag name of the token, then this is a parse error.
Loop: If node is the topmost element in the stack of
open elements, then return. (fragment case)
If node‘s tag name, converted to ASCII lowercase, is
the same as the tag name of the token, pop elements from the stack of open
elements until node has been popped from the stack, and then return.
Set node to the previous entry in the stack of open
elements.
If node is not an element in the HTML namespace, return
to the step labeled loop.
Otherwise, process the token according to the rules given in the section corresponding
to the current insertion mode in HTML content.

13.2.7 The end

Document/DOMContentLoaded_event

Support in all current engines.

Firefox1+Safari3.1+Chrome1+

Opera9+Edge79+

Edge (Legacy)12+Internet Explorer9+

Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Once the user agent stops parsing the document, the user agent
must run the following steps:

Window/load_event

Support in all current engines.

Firefox1+Safari1.3+Chrome1+

Opera4+Edge79+

Edge (Legacy)12+Internet Explorer4+

Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

If the active speculative HTML parser is not null, then stop the
speculative HTML parser and return.
Set the insertion point to undefined.
Update the current document readiness to «interactive«.
Pop all the nodes off the stack of open elements.
While the list of scripts that will execute when the document has finished
parsing is not empty:
1. Spin the event loop until the first script in the list
  of scripts that will execute when the document has finished parsing has its ready
  to be parser-executed set to true and the parser’s Document
  has no style sheet that is blocking scripts.
2. Execute the script element given by the first script in
  the list of scripts that will execute when the document has finished
  parsing.
3. Remove the first script element from the list of scripts that will
  execute when the document has finished parsing (i.e. shift out the first entry in the
  list).
Queue a global task on the DOM manipulation task source given the
Document‘s relevant global object to run the following substeps:
1. Set the Document‘s load timing info’s DOM content loaded
  event start time to the current high resolution time given the
  Document‘s relevant global object.
2. Fire an event named DOMContentLoaded at the Document
  object, with its bubbles attribute initialized to
  true.
3. Set the Document‘s load timing info’s DOM content loaded
  event end time to the current high resolution time given the
  Document‘s relevant global object.
4. Enable the client message queue of the
  ServiceWorkerContainer object whose associated service worker client is the
  Document object’s relevant settings object.
5. Invoke WebDriver BiDi DOM content loaded with the Document‘s
  browsing context, and a new WebDriver BiDi
  navigation status whose id is the
  Document object’s navigation id, status is «pending«, and url is the
  Document object’s URL.
Spin the event loop until the set of scripts that will execute as soon
as possible and the list of scripts that will execute in order as soon as
possible are empty.
Spin the event loop until there is nothing that delays the load event in the Document.
Queue a global task on the DOM manipulation task source given the
Document‘s relevant global object to run the following steps:
1. Update the current document readiness to «complete«.
2. If the Document object’s browsing
  context is null, then abort these steps.
3. Let window be the Document‘s relevant global
  object.
4. Set the Document‘s load timing info’s load event start
  time to the current high resolution time given window.
5. Fire an event named load at window, with legacy target override flag set.
6. Invoke WebDriver BiDi load complete with the Document‘s
  browsing context, and a new WebDriver BiDi
  navigation status whose id is the
  Document object’s navigation
  id, status is «complete«, and url is the Document object’s URL.
7. Set the Document object’s
  navigation id to null.
8. Set the Document‘s load timing info’s load event end
  time to the current high resolution time given window.
9. Assert: Document‘s page showing is
  false.
10. Set the Document‘s page showing flag to true.
11. Fire a page transition event named pageshow at window with false.
12. Completely finish loading the Document.
13. Queue the navigation timing entry for the Document.
If the Document‘s print when loaded flag is set, then run the
printing steps.
The Document is now ready for post-load tasks.

When the user agent is to abort a parser, it must run the following steps:

Throw away any pending content in the input stream, and discard any future
content that would have been added to it.
Stop the speculative HTML parser for this HTML parser.
Update the current document readiness to «interactive«.
Pop all the nodes off the stack of open elements.
Update the current document readiness to «complete«.

13.2.8 Speculative HTML parsing

User agents may implement an optimization, as described in this section, to speculatively fetch
resources that are declared in the HTML markup while the HTML parser is waiting for a
pending parsing-blocking script to be fetched and executed, or during normal parsing,
at the time an element is created for a token.
While this optimization is not defined in precise detail, there are some rules to consider for
interoperability.

Each HTML parser can have an active speculative HTML parser. It
is initially null.

The speculative HTML parser must act like the normal HTML parser (e.g., the
tree builder rules apply), with some exceptions:

The state of the normal HTML parser and the document itself must not be affected.

For example, the next input character or the stack of open
elements for the normal HTML parser is not affected by the speculative HTML
parser.
Bytes pushed into the HTML parser’s input byte stream must also be pushed into
the speculative HTML parser’s input byte stream. Bytes read from the streams must
be independent.
The result of the speculative parsing is primarily a series of speculative fetches. Which kinds of resources to speculatively fetch is
implementation-defined, but user agents must not speculatively fetch resources that
would not be fetched with the normal HTML parser, under the assumption that the script that is
blocking the HTML parser does nothing.

It is possible that the same markup is seen multiple times from the
speculative HTML parser and then the normal HTML parser. It is expected that
duplicated fetches will be prevented by caching rules, which are not yet fully specified.

A speculative fetch for a speculative mock element element
must follow these rules:

Should some of these things be applied to the document «for real», even
though they are found speculatively?

If the speculative HTML parser encounters one of the following elements, then
act as if that element is processed for the purpose of its effect of subsequent speculative
fetches.
- A base element.
- A meta element whose http-equiv
  attribute is in the Content
  security policy state.
- A meta element whose name attribute is an
  ASCII case-insensitive match for «referrer«.
- A meta element whose name attribute is an
  ASCII case-insensitive match for «viewport«. (This can
  affect whether a media query list matches the environment.) [CSSDEVICEADAPT]
Let url be the URL that element would fetch if it was
processed normally. If there is no such URL or if it is the empty string, then do
nothing. Otherwise, if url is already in the list of speculative fetch
URLs, then do nothing. Otherwise, fetch url as if the element was processed
normally, and add url to the list of speculative fetch URLs.

Each Document has a list of speculative fetch URLs, which is a
list of URLs, initially empty.

To start the speculative HTML parser for an instance of an HTML parser
parser:

Optionally, return.

This step allows user agents to opt out of speculative HTML parsing.
If parser‘s active speculative HTML parser is not null, then
stop the speculative HTML parser for parser.

This can happen when document.write()
writes another parser-blocking script. For simplicity, this specification always restarts
speculative parsing, but user agents can implement a more efficient strategy, so long as the end
result is equivalent.
Let speculativeParser be a new speculative HTML parser, with the
same state as parser.
Let speculativeDoc be a new isomorphic representation of parser‘s
Document, where all elements are instead speculative mock elements. Let speculativeParser parse into
speculativeDoc.
Set parser‘s active speculative HTML parser to
speculativeParser.
In parallel, run speculativeParser until it is stopped or until it
reaches the end of its input stream.

To stop the speculative HTML parser for an instance of an HTML parser
parser:

Let speculativeParser be parser‘s active speculative HTML
parser.
If speculativeParser is null, then return.
Throw away any pending content in speculativeParser‘s input
stream, and discard any future content that would have been added to it.
Set parser‘s active speculative HTML parser to null.

The speculative HTML parser will create speculative mock elements instead of normal elements. DOM
operations that the tree builder normally does on elements are expected to work appropriately on
speculative mock elements.

A speculative mock element is a struct with the following items:

A string namespace, corresponding
to an element’s namespace.
A string local name,
corresponding to an element’s local
name.
A list attribute list,
corresponding to an element’s attribute list.
A list children, corresponding to
an element’s children.

To create a speculative mock element given a namespace,
tagName, and attributes:

Let element be a new speculative mock element.
Set element‘s namespace to
namespace.
Set element‘s local name to
tagName.
Set element‘s attribute list
to attributes.
Set element‘s children to a new
empty list.
Optionally, perform a speculative fetch for element.
Return element.

When the tree builder says to insert an element into a template element’s
template contents, if that is a speculative mock element, instead do
nothing. URLs found speculatively inside template elements might themselves be
templates, and must not be speculatively fetched.

13.2.9 Coercing an HTML DOM into an infoset

When an application uses an HTML parser in conjunction with an XML pipeline, it is
possible that the constructed DOM is not compatible with the XML tool chain in certain subtle
ways. For example, an XML toolchain might not be able to represent attributes with the name xmlns, since they conflict with the Namespaces in XML syntax. There is also some
data that the HTML parser generates that isn’t included in the DOM itself. This
section specifies some rules for handling these issues.

If the XML API being used doesn’t support DOCTYPEs, the tool may drop DOCTYPEs altogether.

If the XML API doesn’t support attributes in no namespace that are named «xmlns«, attributes whose names start with «xmlns:«, or
attributes in the XMLNS namespace, then the tool may drop such attributes.

The tool may annotate the output with any namespace declarations required for proper
operation.

If the XML API being used restricts the allowable characters in the local names of elements and
attributes, then the tool may map all element and attribute local names that the API wouldn’t
support to a set of names that are allowed, by replacing any character that isn’t
supported with the uppercase letter U and the six digits of the character’s code point when
expressed in hexadecimal, using digits 0-9 and capital letters A-F as the symbols, in increasing
numeric order.

For example, the element name foo<bar, which can be
output by the HTML parser, though it is neither a legal HTML element name nor a
well-formed XML element name, would be converted into fooU00003Cbar, which
is a well-formed XML element name (though it’s still not legal in HTML by any means).

As another example, consider the attribute xlink:href.
Used on a MathML element, it becomes, after being adjusted, an attribute with a prefix «xlink» and a local
name «href«. However, used on an HTML element, it becomes an attribute with
no prefix and the local name «xlink:href«, which is not a valid NCName, and
thus might not be accepted by an XML API. It could thus get converted, becoming «xlinkU00003Ahref«.

The resulting names from this conversion conveniently can’t clash with any
attribute generated by the HTML parser, since those are all either lowercase or those
listed in the adjust foreign attributes algorithm’s table.

If the XML API restricts comments from having two consecutive U+002D HYPHEN-MINUS characters
(—), the tool may insert a single U+0020 SPACE character between any such offending
characters.

If the XML API restricts comments from ending in a U+002D HYPHEN-MINUS character (-), the tool
may insert a single U+0020 SPACE character at the end of such comments.

If the XML API restricts allowed characters in character data, attribute values, or comments,
the tool may replace any U+000C FORM FEED (FF) character with a U+0020 SPACE character, and any
other literal non-XML character with a U+FFFD REPLACEMENT CHARACTER.

If the tool has no way to convey out-of-band information, then the tool may drop the following
information:

Whether the document is set to no-quirks mode, limited-quirks mode, or
quirks mode
The association between form controls and forms that aren’t their nearest form
element ancestor (use of the form element pointer in the parser)
The template contents of any template elements.

The mutations allowed by this section apply after the HTML
parser’s rules have been applied. For example, a <a::> start tag
will be closed by a </a::> end tag, and never by a </aU00003AU00003A> end tag, even if the user agent is using the rules above to
then generate an actual element in the DOM with the name aU00003AU00003A for
that start tag.

13.2.10 An introduction to error handling and strange cases in the parser

This section is non-normative.

This section examines some erroneous markup and discusses how the HTML parser
handles these cases.

13.2.10.1 Misnested tags: <b><i></b></i>

This section is non-normative.

The most-often discussed example of erroneous markup is as follows:

<p>1<b>2<i>3</b>4</i>5</p>

The parsing of this markup is straightforward up to the «3». At this point, the DOM looks like
this:

html
- head
- body
  - p
    - #text: 1
    - b
      - #text: 2
      - i
        
        #text: 3

Here, the stack of open elements has five elements on it: html,
body, p, b, and i. The list of active
formatting elements just has two: b and i. The insertion
mode is «in body».

Upon receiving the end tag token with the tag name «b», the «adoption
agency algorithm» is invoked. This is a simple case, in that the formatting element is the b element, and there is no furthest block.
Thus, the stack of open elements ends up with just three elements: html,
body, and p, while the list of active formatting elements
has just one: i. The DOM tree is unmodified at this point.

The next token is a character («4»), triggers the reconstruction of the active formatting elements, in this case just
the i element. A new i element is thus created for the «4»
Text node. After the end tag token for the «i» is also received, and the «5»
Text node is inserted, the DOM looks as follows:

html
- head
- body
  - p
    - #text: 1
    - b
      - #text: 2
      - i
        
        #text: 3
    - i
      - #text: 4
    - #text: 5

13.2.10.2 Misnested tags: <b><p></b></p>

This section is non-normative.

A case similar to the previous one is the following:

<b>1<p>2</b>3</p>

Up to the «2» the parsing here is straightforward:

html
- head
- body
  - b
    - #text: 1
    - p
      - #text: 2

The interesting part is when the end tag token with the tag name «b» is parsed.

Before that token is seen, the stack of open elements has four elements on it:
html, body, b, and p. The list of active
formatting elements just has the one: b. The insertion mode is
«in body».

Upon receiving the end tag token with the tag name «b», the «adoption
agency algorithm» is invoked, as in the previous example. However, in this case, there
is a furthest block, namely the p element. Thus, this
time the adoption agency algorithm isn’t skipped over.

The common ancestor is the body element. A conceptual
«bookmark» marks the position of the b in the list of active formatting
elements, but since that list has only one element in it, the bookmark won’t have much
effect.

As the algorithm progresses, node ends up set to the formatting element
(b), and last node ends up set to the furthest block (p).

The last node gets appended (moved) to the common ancestor, so that the DOM looks like:

html
- head
- body
  - b
    - #text: 1
  - p
    - #text: 2

A new b element is created, and the children of the p element are
moved to it:

html
- head
- body
  - b
    - #text: 1
  - p

b
- #text: 2

Finally, the new b element is appended to the p element, so that the
DOM looks like:

html
- head
- body
  - b
    - #text: 1
  - p
    - b
      - #text: 2

The b element is removed from the list of active formatting elements
and the stack of open elements, so that when the «3» is parsed, it is appended to the
p element:

html
- head
- body
  - b
    - #text: 1
  - p
    - b
      - #text: 2
    - #text: 3

13.2.10.3 Unexpected markup in tables

This section is non-normative.

Error handling in tables is, for historical reasons, especially strange. For example, consider
the following markup:

<table><b><tr><td>aaa</td></tr>bbb</table>ccc

The highlighted b element start tag is not allowed directly inside a table like
that, and the parser handles this case by placing the element before the table. (This is
called foster parenting.) This can be seen by examining the DOM tree
as it stands just after the table element’s start tag has been seen:

html
- head
- body
  - table

…and then immediately after the b element start tag has been seen:

html
- head
- body
  - b
  - table

At this point, the stack of open elements has on it the elements
html, body, table, and b (in that order,
despite the resulting DOM tree); the list of active formatting elements just has the
b element in it; and the insertion mode is «in table».

The tr start tag causes the b element to be popped off the stack and
a tbody start tag to be implied; the tbody and tr elements
are then handled in a rather straight-forward manner, taking the parser through the «in table body» and «in row» insertion modes, after which the DOM looks as follows:

html
- head
- body
  - b
  - table
    - tbody
      - tr

Here, the stack of open elements has on it the elements html,
body, table, tbody, and tr; the list of
active formatting elements still has the b element in it; and the
insertion mode is «in row».

The td element start tag token, after putting a td element on the
tree, puts a marker on the list of active
formatting elements (it also switches to the «in
cell» insertion mode).

html
- head
- body
  - b
  - table
    - tbody
      - tr
        
        td

The marker means that when the «aaa» character
tokens are seen, no b element is created to hold the resulting Text
node:

html
- head
- body
  - b
  - table
    - tbody
      - tr
        
        td
        
        #text: aaa

The end tags are handled in a straight-forward manner; after handling them, the stack of
open elements has on it the elements html, body,
table, and tbody; the list of active formatting elements
still has the b element in it (the marker
having been removed by the «td» end tag token); and the insertion mode is «in table body».

Thus it is that the «bbb» character tokens are found. These trigger the «in table text» insertion mode to be used (with the original
insertion mode set to «in table body»).
The character tokens are collected, and when the next token (the table element end
tag) is seen, they are processed as a group. Since they are not all spaces, they are handled as
per the «anything else» rules in the «in table»
insertion mode, which defer to the «in body»
insertion mode but with foster parenting.

When the active formatting elements
are reconstructed, a b element is created and foster parented, and then the «bbb» Text node is appended to it:

html
- head
- body
  - b
  - b
    - #text: bbb
  - table
    - tbody
      - tr
        
        td
        
        #text: aaa

The stack of open elements has on it the elements html,
body, table, tbody, and the new b (again, note
that this doesn’t match the resulting tree!); the list of active formatting elements
has the new b element in it; and the insertion mode is still «in table body».

Had the character tokens been only ASCII whitespace instead of «bbb», then that
ASCII whitespace would just be appended to the tbody element.

Finally, the table is closed by a «table» end tag. This pops all the nodes from
the stack of open elements up to and including the table element, but it
doesn’t affect the list of active formatting elements, so the «ccc» character tokens
after the table result in yet another b element being created, this time after the
table:

html
- head
- body
  - b
  - b
    - #text: bbb
  - table
    - tbody
      - tr
        
        td
        
        #text: aaa
  - b
    - #text: ccc

13.2.10.4 Scripts that modify the page as it is being parsed

This section is non-normative.

Consider the following markup, which for this example we will assume is the document with
URL https://example.com/inner, being rendered as the content of
an iframe in another document with the URL https://example.com/outer:

<div id=a>
 <script>
  var div = document.getElementById('a');
  parent.document.body.appendChild(div);
 </script>
 <script>
  alert(document.URL);
 </script>
</div>
<script>
 alert(document.URL);
</script>

Up to the first «script» end tag, before the script is parsed, the result is relatively
straightforward:

html
- head
- body
  - div id=»a«
    - #text:
    - script
      - #text: var div = document.getElementById(‘a’); ⏎ parent.document.body.appendChild(div);

After the script is parsed, though, the div element and its child
script element are gone:

html
- head
- body

They are, at this point, in the Document of the aforementioned outer
browsing context. However, the stack of open elements still contains
the div element.

Thus, when the second script element is parsed, it is inserted into the outer
Document object.

Those parsed into different Documents than the one the parser was created for do
not execute, so the first alert does not show.

Once the div element’s end tag is parsed, the div element is popped
off the stack, and so the next script element is in the inner
Document:

html
- head
- body
  - script
    - #text: alert(document.URL);

This script does execute, resulting in an alert that says «https://example.com/inner».

13.2.10.5 The execution of scripts that are moving across multiple documents

This section is non-normative.

Elaborating on the example in the previous section, consider the case where the second
script element is an external script (i.e. one with a src attribute). Since the element was not in the parser’s
Document when it was created, that external script is not even downloaded.

In a case where a script element with a src
attribute is parsed normally into its parser’s Document, but while the external
script is being downloaded, the element is moved to another document, the script continues to
download, but does not execute.

In general, moving script elements between Documents is
considered a bad practice.

13.2.10.6 Unclosed formatting elements

This section is non-normative.

The following markup shows how nested formatting elements (such as b) get
collected and continue to be applied even as the elements they are contained in are closed, but
that excessive duplicates are thrown away.

<!DOCTYPE html>
<p><b class=x><b class=x><b><b class=x><b class=x><b>X
<p>X
<p><b><b class=x><b>X
<p></b></b></b></b></b></b>X

The resulting DOM tree is as follows:

DOCTYPE: html
html
- head
- body
  - p
    - b class=»x«
      - b class=»x«
        
        b
        
        b class=»x«
        
        b class=»x«
        
        b
        
        #text: X⏎
  - p
    - b class=»x«
      - b
        
        b class=»x«
        
        b class=»x«
        
        b
        
        #text: X⏎
  - p
    - b class=»x«
      - b
        
        b class=»x«
        
        b class=»x«
        
        b
        
        b
        
        b class=»x«
        
        b
        
        #text: X⏎
  - p
    - #text: X⏎

Note how the second p element in the markup has no explicit b
elements, but in the resulting DOM, up to three of each kind of formatting element (in this case
three b elements with the class attribute, and two unadorned b elements)
get reconstructed before the element’s «X».

Also note how this means that in the final paragraph only six b end tags are
needed to completely clear the list of active formatting elements, even though nine
b start tags have been seen up to this point.

13.3 Serializing HTML fragments

For the purposes of the following algorithm, an element serializes as void if its
element type is one of the void elements, or is basefont,
bgsound, frame, or keygen.

The following steps form the HTML fragment serialization algorithm. The algorithm takes as input a DOM
Element, Document, or DocumentFragment referred to as
the node, and returns a string.

This algorithm serializes the children of the node being serialized, not
the node itself.

If the node serializes as void, then return the empty
string.
Let s be a string, and initialize it to the empty string.
If the node is a template element, then let the node instead be the template element’s template
contents (a DocumentFragment node).
For each child node of the node, in tree order, run the
following steps:
1. Let current node be the child node being processed.
2. Append the appropriate string from the following list to s:
  
  If current node is an Element
  
  If current node is an element in the HTML namespace, the
  MathML namespace, or the SVG namespace, then let tagname be current node‘s local name. Otherwise, let tagname be current node‘s qualified name.
  
  Append a U+003C LESS-THAN SIGN character (<), followed by tagname.
  
  For HTML elements created by the HTML parser or
  createElement(), tagname will be
  lowercase.
  
  If current node‘s is value is not null, and the element does not have an is attribute in its attribute list, then append the string « is="«, followed by current node‘s is value escaped as described below in attribute mode,
  followed by a U+0022 QUOTATION MARK character («).
  
  For each attribute that the element has, append a U+0020 SPACE character, the attribute’s serialized name as described below, a
  U+003D EQUALS SIGN character (=), a U+0022 QUOTATION MARK character («), the
  attribute’s value, escaped as described below in
  attribute mode, and a second U+0022 QUOTATION MARK character («).
  
  An attribute’s serialized name
  for the purposes of the previous paragraph must be determined as follows:
  
  If the attribute has no namespace
  
  The attribute’s serialized name is the attribute’s local name.
  
  For attributes on HTML elements set by the HTML
  parser or by setAttribute(), the
  local name will be lowercase.
  
  If the attribute is in the XML namespace
  
  The attribute’s serialized name is the string «xml:» followed
  by the attribute’s local name.
  
  If the attribute is in the XMLNS namespace and the attribute’s local name
  is xmlns
  
  The attribute’s serialized name is the string «xmlns«.
  
  If the attribute is in the XMLNS namespace and the attribute’s local name
  is not xmlns
  
  The attribute’s serialized name is the string «xmlns:»
  followed by the attribute’s local name.
  
  If the attribute is in the XLink namespace
  
  The attribute’s serialized name is the string «xlink:»
  followed by the attribute’s local name.
  
  If the attribute is in some other namespace
  
  The attribute’s serialized name is the attribute’s qualified name.
  
  While the exact order of attributes is implementation-defined, and may
  depend on factors such as the order that the attributes were given in the original markup,
  the sort order must be stable, such that consecutive invocations of this algorithm serialize
  an element’s attributes in the same order.
  
  Append a U+003E GREATER-THAN SIGN character (>).
  
  If current node serializes as void, then continue on to the next
  child node at this point.
  
  Append the value of running the HTML fragment serialization algorithm on the
  current node element (thus recursing into this algorithm for that
  element), followed by a U+003C LESS-THAN SIGN character (<), a U+002F SOLIDUS character
  (/), tagname again, and finally a U+003E GREATER-THAN SIGN character
  (>).
  
  If current node is a Text node
  
  If the parent of current node is a style,
  script, xmp, iframe, noembed,
  noframes, or plaintext element, or if the parent of current node is a noscript element and scripting is enabled for the node, then append the value of
  current node‘s data literally.
  
  Otherwise, append the value of current node‘s data, escaped as described
  below.
  
  If current node is a
  
  Append the literal string «» (U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS,
  U+003E GREATER-THAN SIGN).
  
  If current node is a ProcessingInstruction
  
  Append the literal string «<?» (U+003C LESS-THAN SIGN, U+003F
  QUESTION MARK), followed by the value of current node‘s target IDL attribute, followed by a single U+0020 SPACE character, followed
  by the value of current node‘s data,
  followed by a single U+003E GREATER-THAN SIGN character (>).
  
  If current node is a DocumentType
  
  Append the literal string «<!DOCTYPE» (U+003C LESS-THAN SIGN, U+0021
  EXCLAMATION MARK, U+0044 LATIN CAPITAL LETTER D, U+004F LATIN CAPITAL LETTER O, U+0043 LATIN
  CAPITAL LETTER C, U+0054 LATIN CAPITAL LETTER T, U+0059 LATIN CAPITAL LETTER Y, U+0050 LATIN
  CAPITAL LETTER P, U+0045 LATIN CAPITAL LETTER E), followed by a space (U+0020 SPACE),
  followed by the value of current node‘s name, followed by the literal string «>» (U+003E GREATER-THAN SIGN).
Return s.

It is possible that the output of this algorithm, if parsed with an HTML
parser, will not return the original tree structure. Tree structures that do not roundtrip
a serialize and reparse step can also be produced by the HTML parser itself, although
such cases are typically non-conforming.

For instance, if a textarea element to which a Comment
node has been appended is serialized and the output is then reparsed, the comment will end up
being displayed in the text control. Similarly, if, as a result of DOM manipulation, an element
contains a comment that contains the literal string «-->«, then when
the result of serializing the element is parsed, the comment will be truncated at that point and
the rest of the comment will be interpreted as markup. More examples would be making a
script element contain a Text node with the text string «</script>«, or having a p element that contains a
ul element (as the ul element’s start
tag would imply the end tag for the p).

This can enable cross-site scripting attacks. An example of this would be a page that lets the
user enter some font family names that are then inserted into a CSS style block via
the DOM and which then uses the innerHTML IDL attribute to get
the HTML serialization of that style element: if the user enters
«</style><script>attack</script>» as a font family name, innerHTML will return markup that, if parsed in a different context,
would contain a script node, even though no script node existed in the
original DOM.

For example, consider the following markup:

<form id="outer"><div></form><form id="inner"><input>

This will be parsed into:

html
- head
- body
  - form id=»outer«
    - div
      - form id=»inner«
        
        input

The input element will be associated with the inner form element.
Now, if this tree structure is serialized and reparsed, the <form id="inner"> start tag will be ignored, and so the input element will be
associated with the outer form element instead.

<html><head></head><body><form id="outer"><div><form id="inner"><input></form></div></form></body></html>

html
- head
- body
  - form id=»outer«
    - div
      - input

As another example, consider the following markup:

<a><table><a>

This will be parsed into:

html
- head
- body
  - a
    - a
    - table

That is, the a elements are nested, because the second a element is
foster parented. After a serialize-reparse roundtrip, the
a elements and the table element would all be siblings, because the
second <a> start tag implicitly closes the first a
element.

<html><head></head><body><a><a></a><table></table></a></body></html>

html
- head
- body
  - a
  - a
  - table

For historical reasons, this algorithm does not round-trip an initial U+000A LINE FEED (LF)
character in pre, textarea, or listing elements, even
though (in the first two cases) the markup being round-tripped can be conforming. The HTML
parser will drop such a character during parsing, but this algorithm does not
serialize an extra U+000A LINE FEED (LF) character.

For example, consider the following markup:

<pre>

Hello.</pre>

When this document is first parsed, the pre element’s child text
content starts with a single newline character. After a serialize-reparse roundtrip, the
pre element’s child text content is simply «Hello.«.

Because of the special role of the is attribute in signaling the creation of customized built-in elements, in that it provides a mechanism for parsed
HTML to set the element’s is
value, we special-case its handling during serialization. This ensures that an element’s
is value is preserved
through serialize-parse roundtrips.

When creating a customized built-in element via the parser, a developer uses the is attribute directly; in such cases serialize-parse roundtrips work fine.

<script>
window.SuperP = class extends HTMLParagraphElement {};
customElements.define("super-p", SuperP, { extends: "p" });
</script>

<div id="container"><p is="super-p">Superb!</p></div>

<script>
console.log(container.innerHTML); // <p is="super-p">
container.innerHTML = container.innerHTML;
console.log(container.innerHTML); // <p is="super-p">
console.assert(container.firstChild instanceof SuperP);
</script>

But when creating a customized built-in element via its constructor or via createElement(), the is
attribute is not added. Instead, the is value (which is what the custom elements machinery uses) is set
without intermediating through an attribute.

<script>
container.innerHTML = "";
const p = document.createElement("p", { is: "super-p" });
container.appendChild(p);

// The is attribute is not present in the DOM:
console.assert(!p.hasAttribute("is"));

// But the element is still a super-p:
console.assert(p instanceof SuperP);
</script>

To ensure that serialize-parse roundtrips still work, the serialization process explicitly
writes out the element’s is
value as an is attribute:

<script>
console.log(container.innerHTML); // <p is="super-p">
container.innerHTML = container.innerHTML;
console.log(container.innerHTML); // <p is="super-p">
console.assert(container.firstChild instanceof SuperP);
</script>

Escaping a string (for the purposes of the algorithm above)
consists of running the following steps:

Replace any occurrence of the «&» character by the string «&«.
Replace any occurrences of the U+00A0 NO-BREAK SPACE character by the string « «.
If the algorithm was invoked in the attribute mode, replace any occurrences of the
«"» character by the string «"«.
If the algorithm was not invoked in the attribute mode, replace any
occurrences of the «<» character by the string «<«, and any occurrences of the «>» character by
the string «>«.

13.4 Parsing HTML fragments

The following steps form the HTML fragment parsing algorithm. The algorithm
takes as input an Element node, referred to as the context element, which gives the context for
the parser, as well as input, a string to parse, and returns a list of zero or
more nodes.

Parts marked fragment case in algorithms in the parser section are
parts that only occur if the parser was created for the purposes of this algorithm. The algorithms have been annotated
with such markings for informational purposes only; such markings have no normative weight. If it
is possible for a condition described as a fragment case to occur even when the
parser wasn’t created for the purposes of handling this algorithm, then that is an error in the
specification.

Create a new Document node, and mark it as being an HTML document.
If the
node document of the context element is in
quirks mode, then let the Document be in quirks mode.
Otherwise, the
node document of the context element is in
limited-quirks mode, then let the Document be in limited-quirks
mode. Otherwise, leave the Document in no-quirks mode.
Create a new HTML parser, and associate it with the just created
Document node.
Set the state of the HTML parser’s tokenization stage as
follows, switching on the context element:

title

textarea

Switch the tokenizer to the RCDATA state.

style

xmp

iframe

noembed

noframes

Switch the tokenizer to the RAWTEXT state.

script

Switch the tokenizer to the script data state.

noscript

If the scripting flag is enabled, switch the tokenizer to the RAWTEXT
state. Otherwise, leave the tokenizer in the data state.

plaintext

Switch the tokenizer to the PLAINTEXT state.

Any other element

Leave the tokenizer in the data state.

For performance reasons, an implementation that does not report errors and
that uses the actual state machine described in this specification directly could use the
PLAINTEXT state instead of the RAWTEXT and script data states where those are mentioned in the
list above. Except for rules regarding parse errors, they are equivalent, since there is no
appropriate end tag token in the fragment case, yet they involve far fewer state
transitions.
Let root be a new html element with no attributes.
Append the element root to the Document node created
above.
Set up the parser’s stack of open elements so that it contains just the single
element root.
If the context element is a
template element, push «in
template» onto the stack of template insertion modes so that it is the new
current template insertion mode.
Create a start tag token whose name is the local name of context and whose attributes are the attributes of
context.

Let this start tag token be the start tag token of the context node, e.g. for the purposes of determining
if it is an HTML integration point.
Reset the parser’s insertion mode
appropriately.

The parser will reference the context element as part of that algorithm.
Set the parser’s form element pointer to the nearest node to the
context element that is a form
element (going straight up the ancestor chain, and including the element itself, if it is a
form element), if any. (If there is no such form element, the
form element pointer keeps its initial value, null.)
Place the input into the input stream for the HTML
parser just created. The encoding confidence is irrelevant.
Start the parser and let it run until it has consumed all the characters just inserted into
the input stream.
Return the child
nodes of root, in tree order.

Источник

Большинство ошибок, возникающих при валидации кода можно свести к набору типовых вариантов, зная которые легко понять, на что «намекает» валидатор. В качестве образца возьмем расширение HTML Validator для браузера Firefox, предназначенное для проверки кода и рассмотрим список ошибок и замечаний по коду.

Посмотреть все возможные сообщения валидатора можно по адресу http://www.htmlpedia.org/wiki/HTML_Tidy, далее приведены основные ошибки с их описанием и решением. Зеленым цветом выделен корректный вариант, другой цвет используется для обозначения ошибки.

Notice: entity «…» doesn’t end in «;»

Это замечание возникает при использовании спецсимволов вроде < при отсутствии на конце точки с запятой.

&nbsp

Решение

Добавьте в конце спецсимвола точку с запятой.

Notice: numeric character reference «…» doesn’t end in ‘;’

Возникает при использовании числовых спецсимволов вроде — когда в конце забыли добавить точку с запятой.

™

&#8482

Решение

Добавьте в конце спецсимвола точку с запятой.

unescaped & or unknown entity «&…»

Символ амперсанда (&) часто применяется в адресах ссылок (атрибут href тега <a>), поскольку он разделяет несколько параметров. Однако амперсанд зарезервирован для спецсимволов вроде   поэтому в ссылках необходимо указывать & вместо &.

<a href=»http://www.htmlbook.ru/content/?id=30&text=1″>Ссылка</a>

Решение

Замените & на &.

missing </…>

Отсутствует обязательный закрывающий тег.

<head><title>Заголовок</title></head>

<head><title>Заголовок</head>

Решение

Добавьте закрывающий тег.

missing </aaa> before <bbb>

Ошибка возникает при нарушении порядка тегов, когда блочный тег располагается внутри встроенного. В данном случае блочный тег <bbb> находится внутри встроенного тега <aaa>.

<p><span>Текст</span></p>

<span><p>Текст</p></span>

Решение

Поменяйте расположение тегов — перенесите встроенный тег внутрь блочного.

discarding unexpected <…>

Обнаружен открывающий или закрывающий тег, у которого нет пары. Подобная ошибка возникает в двух случаях: есть открывающий тег, но нет закрывающего; имеется закрывающий тег, которому не соответствует открывающий.

<div><div>Текст</div></div>

<div>Текст</div></div>

<div><div>Текст</div>

Решение

В зависимости от ситуации добавьте или удалите открывающий или закрывающий тег.

Notice: nested emphasis …

Контейнер содержит аналогичный тег физического форматирования, который не должен повторяться.

<p><b>Текст</b></p>

<p><b><b>Текст</b></b></p>

Решение

Удалите один из тегов.

replacing unexpected … by </…>

Закрывающий тег не соответствует открывающему тегу.

<p><b>Текст</b></p>

<p><b>Текст</span></p>

Решение

Замените открывающий или закрывающий тег на парный.

… isn’t allowed in <…> elements

Обнаружены теги, которые запрещено размещать внутри указанных элементов.

<head><title>Заголовок</title></head>

<head><body>Текст</body></head>

Решение

Переместите HTML-элемент в правильный раздел.

missing <…>

Нет обязательного тега в структуре элементов. Ошибка, к примеру, может возникнуть при формировании таблицы, когда пропущен тег <tr> и сразу же после <table> следует <td>.

<ol><li>Список</li></ol>

<ol>Список</ol>

Решение

Проверить правильность вложения тегов в текущем элементе и наличие обязательных элементов.

Notice: inserting implicit <…>

Сообщение возникает из-за предыдущей ошибки на странице.

Решение

Исправьте предыдущие ошибки.

Insert missing <title> element

В коде не вставлен тег <title>.

<head><title>Заголовок</title></head>

Решение

Добавьте контейнер <title>.

Multiple <frameset> elements

Тег <frameset> используется в документе более одного раза без вложения. Допускается вставлять несколько элементов <frameset>, но вложенных один в другой.

Решение

Используйте вложенные теги <frameset>.

<…> is not approved by W3C

Указанный тег не входит в спецификацию HTML.

<span style=»white-space: nowrap;»>текст без переносов</span>

<nobr>текст без переносов</nobr>

Решение

Удалите тег или замените его подходящим эквивалентом.

Error: <…> is not recognized!

Тег не распознан и не входит в спецификацию HTML.

Правильно: <p>Текст</p>

Неверно: <p><adres>Текст</adres></p>

Решение

Удалите неизвестный тег.

Trimming Empty Tag

Контейнер пустой или содержит только пробел.

<p>Текст</p>

<p></p>

Решение

Удалите тег или добавьте внутрь контейнера текст.

<a> is probably intended as </a>

В закрывающем теге <a> отсутствует слэш.

<a href=»http://htmlbook.ru»>Ссылка на сайт</a>

<a href=»http://htmlbook.ru»>Ссылка на сайт<a>

Решение

Добавьте слэш к закрывающему тегу.

… shouldn’t be nested

Некоторые теги вроде <form> не могут содержать сами себя. Это сообщение также возникает из-за предыдущей ошибки.

Решение

Удалите вложенные теги или исправьте предыдущую ошибку.

Text found after closing </body>-tag

Теги или текст добавляется после закрывающего тега </body>.

<html>
<head><title>Заголовок</title></head>
<body><p>Основной текст</p></body>
</html>

<html>
<head><title>Заголовок</title></head>
<body><p>Основной текст</p></body>
<b>Привет!</b>
</html>

Решение

Удалите текст после тега </body> или перенесите этот тег в конец текста.

Adjacent hyphens within comment

Комментарии в коде HTML определяются конструкцией вида <!— комментарий —>. Если в тексте комментария подряд идет два и более дефиса, возникает ошибка.

<!— Комментарий — заголовок —>

<!— комментарий —>

<!— Комментарий — тело документа —>

Решение

Удалите лишние дефисы.

SYSTEM, PUBLIC, W3C, DTD, EN must be upper case

Элемент <!DOCTYPE> указан неверно, в частности следующие атрибуты необходимо писать в верхнем регистре: SYSTEM, PUBLIC, W3C, DTD, EN.

<!DOCTYPE HTML PUBLIC «-//W3C//DTD HTML 4.01 Transitional//EN» «http://www.w3.org/TR/html4/loose.dtd»>

<!doctype html public «-//w3c//dtd html 4.01 Transitional//en» «http://www.w3.org/TR/html4/loose.dtd»>

Решение

Пишите <!DOCTYPE> корректно.

Warning: missing <!DOCTYPE> declaration

Не указан элемент <!DOCTYPE>.

<!DOCTYPE HTML PUBLIC «-//W3C//DTD HTML 4.01//EN» «http://www.w3.org/TR/html4/strict.dtd»>
<html>
<head>
<title>Заголовок</title>
</head>
<body>
<p>Основной текст</p>
</body>
</html>

<html>
<head>
<title>Untitled Document</title>
</head>
<body>
</body>
</html>

Решение

Поместите элемент <!DOCTYPE> в самую первую строку кода документа.

Too much <…>-elements

Повторяется тег, который в коде должен быть только один. К таким тегам относится <html>, <head>, <title> и <body>.

<head>
<title>Заголовок</title>
</head>

<head>
<title>Заголовок</title>
<title>Название статьи</title>
</head>

Решение

Удалите повторяющийся тег.

<…> inserting «…» attribute

Не указан обязательный атрибут для данного тега.

<style>

Решение

Проверьте тег и добавьте недостающие атрибуты.

… attribute … lacks value

Атрибут тега не содержит обязательное значение или оно написано с синтаксической ошибкой.

<a href=»link.html»>Ссылка</a>

<a href>Ссылка</a>

Решение

Проверьте атрибуты тега и добавьте недостающие значения.

… attribute «…» has invalid value «…»

Атрибут содержит некорректное значение. Ошибка проявляется в тех случаях, когда в значении вместо текста пишется число и наоборот. Так, атрибуты id и name должны начинаться с символа ([A-Za-z]) и могут содержать цифры ([0-9]), дефис (-), подчеркивание (_), двоеточие (:) и точку (.). Значение ширины и высоты в атрибутах тегов не должно содержать ничего, кроме цифр ([0-9]) и процентов (%).

Решение

Проверьте атрибут тега и измените его значение.

<…> missing > for end of tag

Ошибка может возникать в двух случаях: некорректно написан тег, что происходит, когда забыли добавить закрывающую скобку и применение > вместо использования спецсимвола.

<p>Пример текста</p>

<p>Для случая 0<p рассмотрим следующий пример.</p>

<p>Для случая 0<p рассмотрим следующий пример.</p>

Решение

Вставьте отсутствующую закрывающую скобку.
Замените < на <.

<…> proprietary attribute «…»

Тег содержит атрибут, специфичный только для браузера Internet Explorer или другого и не входящий в спецификацию. Примером является атрибут height тега <table>.

Список всех атрибутов, входящих в спецификацию HTML приведен по адресу http://www.w3.org/TR/html4/index/attributes.html

Решение

Список наиболее характерных атрибутов тегов приведен в табл. 14.1.

Табл. 14.1. Замена нестандартных атрибутов тегов

Тег	Устаревший атрибут	Стандартный атрибут
<body>	marginwidth=0, marginheight=0, leftmargin=0, topmargin=0	style=»margin: 0″
<table>	height=100%	style=»height: 100%»
<table>	nowrap	style=»white-space: nowrap» или <td nowrap>
<td>	background=»abc.gif»	style=»background-image:url(abc.gif)»

… proprietary attribute value «…»

Значение атрибута не входит в спецификацию HTML и является специфичным для браузера Internet Explorer или другого. Например, значение align=»absmiddle» тега <img> недопустимо.

Решение

Используйте стандартные значения атрибутов тегов или используйте стилевой эквивалент.

… dropping value «…» for repeated attribute «…»

Атрибут применяется в теге больше одного раза.

Решение

Удалите повторяющийся атрибут.

… unexpected or duplicate quote mark

Отсутствует открывающая или закрывающая кавычка в атрибуте тега.

Решение

Добавьте парную кавычку к значению атрибута.

… attribute with missing trailing quote mark

Тег содержит атрибут, в котором задано неверное количество кавычек.

Решение

Добавьте или удалите одну из кавычек.

… id and name attribute value mismatch

Ошибка возникает, когда значения атрибутов id и name не совпадают между собой, что приводит к конфликту при обращении к свойствам элемента через скрипты.

Решение

Удалите один из атрибутов или сделайте значения атрибутов name и id одинаковыми.

Notice: replacing <…> by <…>

Ошибка возникает в следующих случаях:

неверный порядок тегов;
добавлен лишний закрывающий тег;
имеется открывающий тег без наличия обязательного закрывающего.

<p>Текст</p><br>

<p>Текст</p></p>

Решение

Измените порядок тегов или удалите один из открывающих или закрывающих тегов.

… anchor «…» already defined

Значения атрибута name у различных тегов совпадает между собой. Значение name должно быть уникальным.

Решение

Выберите другое имя или измените предыдущие имена таким образом, чтобы они не совпадали.

<…> is probably intended as </…>

Тег повторяется дважды в коде HTML, тогда как подобный тег не должен содержать сам себя.

<em>Привет, мир!</em>

<em>Привет<em>, мир!</em></em>

Решение

Удалите один из тегов.

<…> lacks «…» attribute

Требуется обязательный атрибут тега, который, тем не менее, отсутствует.

<form>

Решение

Добавьте недостающий атрибут к тегу.

Источник

I am making a web page and I am nearing completion, so I decided to put it through an html validator, and I had a bunch of errors with my page. My page works currently with <!DOCTYPE xhtml><html>... but when I type <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> my page’s spacing breaks.

Examples: Picture of when it works

Code: <!DOCTYPE xhtml> <html ng-app="ticTacToe" xmlns="http://www.w3.org/1999.xhtml">

What happens when I add the proper code:

Code:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html ng-app="ticTacToe" xmlns="http://www.w3.org/1999.xhtml">

So my question is, how can I make the spacing work, with the more valid code? It looks like the CSS selector «top: » that I am using is not working. Any feedback will be greatly appreciated. Let me know if you need more info, thanks in advance!

UPDATE: Direct CSS that is responsible for that part

#bodyArea
{
    width: 425px;
    position: relative;
    top: 30%;
    left: 40%;
}

Источник

Тег DOCTYPE означает «объявление типа документа». Он сообщает веб-браузерам, какую версию HTML использует ваша страница. Прописывать DOCTYPE необходимо для переключения браузера в режим соответствия стандартам данной версии. DOCTYPE всегда должен быть самой первой строкой HTML-кода страницы.

Хотя современные браузеры не принимают во внимание незначительные ошибки в коде HTML, неправильный DOCTYPE является серьезной проблемой, которая может существенно повлиять на доступность вашего веб-контента. Отчет Labrika «Неверный HTML DOCTYPE» позволяет установить наличие таких ошибок.

Содержание отчета

Отчет показывает список URL-адресов страниц, в HTML-коде которых DOCTYPE прописан неверно.

Использование отчета

Найдите страницы с некорректным DOCTYPE и пропишите его правильно.

Синтаксис:

<!DOCTYPE [Элемент верхнего уровня] [Публичность] "[Регистрация]//[Организация]//[Тип] [Имя]//[Язык]" "[URL]">

Параметры:

Элемент верхнего уровня — указывает элемент верхнего уровня в документе, для HTML это тег <html>.
Публичность — указывает, является объект публичным (значение PUBLIC) или системным (значение SYSTEM) ресурсом, например, таким как локальный файл. Для HTML/XHTML выбирается значение PUBLIC.
Регистрация — сообщает, зарегистрирован ли разработчик DTD (document type definition, описания типа документа) в международной организации по стандартизации (International Organization for Standardization, ISO). Принимает одно из двух значений: плюс (+) — разработчик зарегистрирован в ISO или минус (-) — разработчик не зарегистрирован. Для W3C указывается значение «-».
Организация — уникальное название организации, разработавшей DTD. Официально HTML/XHTML публикует W3C (англ. World Wide Web Consortium — Консорциум Всемирной паутины). Нназвание этой организации и пишется в теге DOCTYPE.
Тип описываемого документа. Для HTML/XHTML указывается значение DTD.
Имя — уникальное имя документа для описания DTD.
Язык — указывается язык, на котором написан текст для описания объекта. Содержит две буквы, пишется в верхнем регистре. Для документа HTML/XHTML нужно прописывать английский язык (EN).
URL — адрес документа с DTD.

Существует несколько видов DOCTYPE — они различаются в зависимости от используемой на странице версии языка разметки гипертекста.

Пример для версии HTML 4.01:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

Спецификация HTML5 предлагает следующий вариант написания DOCTYPE для всех документов:

<!DOCTYPE html>.

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