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<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>CSS Syntax Module Level 3 (CSS3 Syntax)</title>
<link rel=contents href="#contents">
<link rel=index href="#index">
<link rel="stylesheet" type="text/css" href="../default.css">
<link rel="stylesheet" type="text/css"
href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css">
<style type="text/css">
/* delete this block when you've cleared out all the .replaceme elements */
.replaceme {
border: solid red;
padding: 0 0.5em;
margin: 0 0.1em;
background: yellow;
color: green;
}
.replaceme:before {
content: "FIXME(";
color: black;
}
.replaceme:after {
content: ")";
color: black;
}
</style>
</head>
<div class="head">
<!--logo-->
<h1>CSS Syntax Module Level 3</h1>
<h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
<dl>
<dt>This version:
<dd>
<a href="http://dev.w3.org/csswg/css3-syntax/">http://dev.w3.org/csswg/css3-syntax/</a>
<!--
<dt>Latest version:
<dd>
<a href="http://www.w3.org/TR/css3-syntax/">http://www.w3.org/TR/css3-syntax/</a>
-->
<dt>Editor's draft:
<dd>
<a href="http://dev.w3.org/csswg/css3-syntax/">http://dev.w3.org/csswg/css3-syntax/</a>
<dt>Previous version:
<dd>
<a href="http://www.w3.org/TR/2003/WD-css3-syntax-20030813/">http://www.w3.org/TR/2003/WD-css3-syntax-20030813/</a>
<dt>Issue Tracking:
<dd>
<a href="https://www.w3.org/Bugs/Public/buglist.cgi?product=CSS&component=Syntax">W3C Bugzilla</a>
<dt>Feedback:
<dd>
<a href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>
with subject line “<kbd>[css3-syntax] <var>… message topic …</var></kbd>”
<dt>Editors:
<dd class="h-card vcard">
<a class="p-name fn u-url url" rel="author"
href="http://www.xanthir.com/">Tab Atkins Jr.</a>
(<span class="p-org org">Google, Inc.</span>),
<span class="u-email email">jackalmage@gmail.com</span>
</dl>
<!--copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id="abstract">Abstract</h2>
<p>
<a href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, in speech, etc.
This module describes, in general terms, the basic structure and syntax of CSS stylesheets.
It defines, in detail, the syntax and parsing of CSS - how to turn a stream of bytes into a meaningful stylesheet.
<h2 class="no-num no-toc" id="status">Status of this document</h2>
<!--status-->
<p>The following features are at risk: …
<h2 class="no-num no-toc" id="contents">
Table of contents</h2>
<!--toc-->
<h2 id="intro">
Introduction</h2>
<p><em>This section is not normative.</em>
<p><var class="replaceme">Provide background, motivation, etc.</var></p>
<h3 id="placement">
Module interactions</h3>
<p>
This module defines the syntax and parsing of CSS stylesheets.
It supersedes the lexical scanner and grammar defined in CSS 2.1.
<h2 id='syntax-description'>
Description of CSS's Syntax</h2>
<p><em>This section is not normative.</em>
<p>
A CSS document is a series of <i>rules</i>,
which apply CSS properties to elements in the source document,
and <i>at-rules</i>,
which define special processing rules or values for the CSS document.
<p>
A <dfn>rule</dfn> starts with a selector
(defined by the <a href="http://www.w3.org/TR/selectors/">Selectors specification</a>),
then has a {}-wrapped block containing a sequence of declarations.
The selector specifies which elements the declarations will apply to.
Each declaration has a property name,
followed by a colon and the property value,
and finished with a semicolon.
<div class='example'>
<p>
A typical rule might look something like this:
<pre>
p > a {
color: blue;
text-decoration: underline;
}</pre>
<p>
In the above rule, "<code>p > a</code&
8096
gt;" is the selector,
which, if the source document is HTML,
selects any <code><a></code> elements that are children of a <code><p></code> element.
<p>
"<code>color: blue;</code>" is a declaration specifying that,
for the elements that match the selector,
their 'color' property should have the value ''blue''.
Similiarly, their 'text-decoration' property should have the value ''underline''.
</div>
<p>
<dfn title="at-rule">At-rules</dfn> are all different, but they have a basic structure in common.
They start with an "@" character followed by their name.
Some <i>at-rules</i> are simple statements,
with their name followed by more CSS values to specify their behavior,
and finally ended by a semicolon.
Others are blocks;
they can have CSS values following their name,
but they end with a {}-wrapped block,
similar to a <i>rule</i>.
Even the contents of these blocks are specific to the given <i>at-rule</i>:
sometimes they contain a sequence of declarations, like a <i>rule</i>;
other times, they may contain additional blocks, or at-rules, or other structures altogether.
<div class='example'>
<p>
Here are several examples of <i>at-rules</i> that illustrate the varied syntax they may contain.
<pre>@import "my-styles.css";</pre>
<p>
The ''@import'' <i>at-rule</i> is a simple statement.
After its name, it takes a single string or ''url()'' function to indicate the stylesheet that it should import.
<pre>
@page :left {
margin-left: 4cm;
margin-right: 3cm;
}</pre>
<p>
The ''@page'' <i>at-rule</i> consists of an optional page selector (the ":left" pseudoclass),
followed by a block of properties that apply to the page when printed.
In this way, it's very similar to a normal <i>rule</i>,
except that its properties don't apply to any "element",
but rather the page itself.
<pre>
@media print {
body { font-size: 10pt }
}</pre>
<p>
The ''@media'' <i>at-rule</i> begins with a media type
and a list of optional media queries.
Its block contains entire rules,
which are only applied when the ''@media''s conditions are fulfilled.
</div>
<p>
Property names and <i>at-rule</i> names are always <b>identifiers</b>,
which have to start with a letter or a hyphen followed by a letter,
and then can contain letters, numbers, hyphens, or underscores.
You can include any character at all,
even ones that CSS uses in its syntax,
by escaping it with a backslash (\) or by using a hexadecimal escape.
<p>
The syntax of selectors is defined in the <a href="http://www.w3.org/TR/selectors/">Selectors spec</a>.
Similarly, the syntax of the wide variety of CSS values is defined in the <a href="http://www.w3.org/TR/css3-values/">Values & Units spec</a>.
The special syntaxes of individual <i>at-rules</i> can be found in the specs that define them.
<h2>
Tokenizing and Parsing CSS</h2>
<p>
User agents must use the parsing rules described in this section to generate the CSSOM trees from text/css resources.
Together, these rules define what is referred to as the CSS parser.
<p>
This specification defines the parsing rules for CSS 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:
user agents must either act as described below when encountering such problems,
or must abort processing at the first error that they encounter for which they do not wish to apply the rules described below.
<p>
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.
Conformance checkers are not required to recover from parse errors.
<h3>
Overview of the Parsing Model</h3>
<p>
The input to the CSS parsing process consists of a stream of Unicode code points,
which is passed through a tokenization stage followed by a tree construction stage.
The output is a CSSStyleSheet object.
<p class='note'>
Implementations that do not support scripting do not have to actually create a CSSOM CSSStyleSheet object,
but the CSSOM tree in such cases is still used as the model for the rest of the specification.
<h3>
The input byte stream</h3>
<p>
The stream of Unicode 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 must use to decode the bytes into characters.
<p>
The <i>encoding sniffing algorithm</i> defined below is used to determine the character encoding.
<p>
Given an encoding,
the bytes in the input byte stream must be converted to Unicode code points for the tokenizer's input stream,
as described by the rules for that encoding,
except that the leading U+FEFF BYTE ORDER MARK character, if any,
must not be stripped by the encoding layer (
133E
it is stripped by the rule below).
<p>
Bytes or sequences of bytes in the original byte stream that could not be converted to Unicode code points
must be converted to U+FFFD REPLACEMENT CHARACTERs.
Specifically,
if the encoding is UTF-8,
the bytes must be decoded with the error handling defined in this specification.
<p class='note'>
Bytes or sequences of bytes in the original byte stream that did not conform to the encoding specification
(e.g. invalid UTF-8 byte sequences in a UTF-8 input byte stream)
are errors that conformance checkers are expected to report.
<h4>
Determining the character encoding</h4>
<div class='issue'>
<p>
General algorithm:
<ol>
<li>
If the stylesheet is embedded,
the charset is the charset of the outer document.
<li>
If the resource carried a Charset header,
and the value of the header is a valid charset,
that's the charset of the stylesheet.
<li>
If the document contains an @charset rule at the very top
(specify how to parse this in the presence of arbitrary charsets)
and it specifies a valid charset,
that's the charset of the stylesheet.
<li>
The charset is UTF-8.
</ol>
</div>
<h4>
Preprocessing the input stream</h4>
<p>
The input stream consists of the characters pushed into it as the input byte stream is decoded.
<p>
One leading U+FEFF BYTE ORDER MARK character must be ignored if any are present in the input stream.
<p class='note'>
The requirement to strip a U+FEFF BYTE ORDER MARK character regardless of whether that character was used to determine the byte order is a willful violation of Unicode, motivated by a desire to increase the resilience of user agents in the face of naïve transcoders.
<p>
U+000D CARRIAGE RETURN (CR) characters and U+000A LINE FEED (LF) characters are treated specially. All CR characters must be converted to LF characters, and any LF characters that immediately follow a CR character must be ignored. Thus, newlines in CSS stylesheets are represented by LF characters, and there are never any CR characters in the input to the tokenization stage.
<p>
The <dfn>next input character</dfn> 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 <i>next input character</i> is the first character in the input. The <dfn>current input character</dfn> is the last character to have been consumed.
<p>
The "EOF" character in the tables below is a conceptual character representing the end of the input stream.
<h3>
Parse State</h3>
<p>
...
<h3>
Tokenization</h3>
<p>
Implementations must act as if they used the following state machine to tokenize CSS.
The state machine must start in the <i>data state</i>.
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 same 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.
<p>
The output of the tokenization step is a series of zero or more of the following tokens:
identifier,
function,
at-keyword,
hash,
string,
bad-string,
url,
bad-url,
delim,
number,
percentage,
dimension,
unicode-range,
whitespace,
comment,
cdo,
cdc,
colon,
semicolon,
[,
],
(,
),
{,
}.
<p>
Identifier, function, at-keyword, hash, string, and url tokens have a value composed of zero or more characters.
Delim tokens have a value composed of a single character.
Number, percentage, and dimension tokens have a representation composed of 1 or more character, a numeric value, and a type flag set to either "integer" or "number". The type flag defaults to "integer" if not otherwise set.
Dimension tokens additionally have a unit composed of one or more characters.
Unicode-range tokens have a range of characters.
<p>
The tokenizer state machine consists of the states defined in the following subsections.
<h4>
Tokenizer Flags</h4>
<p>
The tokenizer can be run with any of several flags that alter its behavior.
<dl>
<dt>the <dfn>transform function whitespace</dfn> flag
<dd>
This flag is set when parsing SVG's <code>transform</code> attribute.
When this is set, whitespace is allowed between the name of a transform function and its opening parenthesis.
<dt>the <dfn>quirks mode</dfn> flag
<dd>
This flag is set when the host document is in quirks mode.
When this is set,
the parser allows <a href="#consume-a-primitive-with-the-hashless-co">hash colors without the # character</a>
and <a href="#consume-a-primitive-with-the-unitless-le">pixel lengths without the 'px' unit</a>
in some circumstances.
</dl>
<h4>
Definitions</h4>
<p>
This section defines several terms used during the tokenization phase.
<dl>
<dt><dfn>digit</dfn>
<dd>
A character between U+0030 DIGIT ZERO (0) and U+0039 DIGIT NINE (9).
<dt><dfn>hex digit</dfn>
<dd>
A <i>digit</i>,
or a character between U+0041 LATIN CAPITAL LETTER A (A) and U+0046 LATIN CAPITAL LETTER F (F),
or a character between U+0061 LATIN SMALL LETTER A (a) and U+0066 LATIN SMALL LETTER F (f).
<dt><dfn>uppercase letter</dfn>
<dd>
A character between U+0041 LATIN CAPITAL LETTER A (A) and U+005A LATIN CAPITAL LETTER Z (Z).
<dt><dfn>lowercase letter</dfn>
<dd>
A character between U+0061 LATIN SMALL LETTER A (a) and U+007A LATIN SMALL LETTER Z (z).
<dt><dfn>letter</dfn>
<dd>
An <i>uppercase letter</i>
or a <i>lowercase letter</i>.
<dt><dfn>non-ASCII character</dfn>
<dd>
A character with a codepoint equal to or greater than U+00A0 NO-BREAK SPACE.
<dt><dfn>name-start character</dfn>
<dd>
A <i>letter</i>,
a <i>non-ASCII character</i>,
or U+005F LOW LINE (_).
<dt><dfn>name character</dfn>
<dd>
A <i>name-start character</i>,
A <i>digit</i>,
or U+002D HYPHEN-MINUS (-).
<dt><dfn>non-printable character</dfn>
<dd>
A character between U+0000 NULL and U+0008 BACKSPACE
or a character between U+000E SHIFT OUT and U+001F INFORMATION SEPARATOR ONE
or a character between U+007F DELETE and U+009F APPLICATION PROGRAM COMMAND.
<dt><dfn>newline</dfn>
<dd>
U+000A LINE FEED or U+000C FORM FEED.
<span class='note'>
Note that U+000D CARRIAGE RETURN is not included in this definition,
as it is removed from the stream during preprocessing.
</span>
<dt><dfn>whitespace</dfn>
<dd>A <i>newline</i>, U+0009 CHARACTER TABULATION, or U+0020 SPACE.
<dt><dfn>maximum allowed codepoint</dfn>
<dd>The greatest codepoint defined by Unicode. This is currently U+10FFFF.
</dl>
<h4>
<dfn>Data state</dfn></h4>
<p>
Consume the <i>next input character</i>.
<dl>
<dt><i>whitespace</i>
<dd>
Consume as much <i>whitespace</i> as possible.
Emit a whitespace token.
Remain in this state.
<dt>U+0022 QUOTATION MARK (")
<dd>
Switch to the <i>double-quote-string state</i>.
<dt>U+0023 NUMBER SIGN (#)
<dd>
Switch to the <i>hash state</i>.
<dt>U+0027 APOSTROPHE (')
<dd>
Switch to the <i>single-quote-string state</i>.
<dt>U+0028 LEFT PARENTHESIS (()
<dd>
Emit a ( token.
Remain in this state.
<dt>U+0029 RIGHT PARENTHESIS ())
<dd>
Emit a ) token.
Remain in this state.
<dt>U+002B PLUS SIGN (+)
<dd>
If the <i>next input character</i> is
a <i>digit</i>,
or the <i title="next input character">next 2 input characters</i> are
U+002E FULL STOP (.)
followed by a <i>digit</i>,
switch to the <i>number state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
emit a delim token
with its value set to U+002B PLUS SIGN (+).
Remain in this state.
<dt>U+002D HYPHEN-MINUS (-)
<dd>
If the <i title="next input character">next 2 input characters</i> are
U+002D HYPHEN-MINUS
U+003E GREATER-THAN SIGN
(->),
consume them,
emit a CDC token,
and remain in this state.
<p>
Otherwise,
if the <i>next input character</i> is
a <i>digit</i>,
or the <i title="next input character">next 2 input characters</i> are
U+002E FULL STOP (.)
followed by a <i>digit</i>,
switch to the <i>number state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
if the <i>next input character</i> is
a <i>name-start character</i>,
switch to the <i>identifier state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
emit a delim token
with its value set to U+002D HYPHEN-MINUS (-).
Remain in this state.
<dt>U+002E FULL STOP (.)
<dd>
If the <i>next input character</i> is a digit,
switch to the <i>number state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
emit a delim token
with its value set to U+002E FULL STOP (.).
Remain in this state.
<dt>U+002F SOLIDUS (/)
<dd>
If the <i>next input character</i> is U+002A ASTERISK (*),
consume it
and switch to the <i>comment state</i>.
<p>
Otherwise,
emit a delim token
with its value set to U+002F SOLIDUS (/).
Remain in this state.
<dt>U+003A COLON (:)
<dd>
Emit a colon token.
Remain in this state.
<dt>U+003B SEMICOLON (;)
<dd>
Emit a semicolon token.
Remain in this state.
<dt>U+003C LESS-THAN SIGN (<)
<dd>
If the <i title="next input character">next 3 input characters</i> are
U+0021 EXCLAMATION MARK
U+002D HYPHEN-MINUS
U+002D HYPHEN-MINUS
(!--),
consume them
and emit a cdo token.
Remain in this state.
<p>
Otherwise,
emit a delim token
with its value set to U+003C LESS-THAN SIGN (<).
Remain in this state.
<dt>U+0040 COMMERCIAL AT (@)
<dd>
Switch to the <i>at-keyword state</i>.
<dt>U+005B LEFT SQUARE BRACKET ([)
<dd>
Emit a [ token.
Remain in this state.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i> is
a <i>newline</i>
or EOF,
this is a <i>parse error</i>.
Emit a delim token
with its value set to U+005C REVERSE SOLIDUS (\).
Remain in this state.
<p>
Otherwise, switch to the <i>identifier state</i>.
Reconsume the <i>current input character</i>.
<dt>U+005D RIGHT SQUARE BRACKET (])
<dd>
Emit a ] token.
Remain in this state.
<dt>U+007B LEFT CURLY BRACKET ({)
<dd>
Emit a [ token.
Remain in this state.
<dt>U+007D RIGHT CURLY BRACKET (})
<dd>
Emit a } token.
Remain in this state.
<dt><i>digit</i>
<dd>
Switch to the <i>number state</i>.
Reconsume the <i>current input character</i>.
<dt>U+0055 LATIN CAPITAL LETTER U (U)
<dt>U+0075 LATIN SMALL LETTER U (u)
<dd>
If the <i title="next input character">next 2 input character</i> are
U+002B PLUS SIGN (+)
followed by a <i>hex digit</i>,
consume the <i>next input character</i>.
<span class='note'>Note: don't consume both of them.</span>
Switch to the <i>unicode-range state</i>.
<p>
Otherwise,
if the <i title="next input character">next 3 input characters</i> are
U+0052 LATIN CAPITAL LETTER R (R) or U+0072 LATIN SMALL LETTER R (r)
followed by U+004C LATIN CAPITAL LETTER L (L) or U+006C LATIN SMALL LETTER L (l)
followed by U+0028 LEFT PARENTHESIS ((),
consume them.
Switch to the <i>url state</i>.
<p>Otherwise,
switch to the <i>identifier state</i>.
Reconsume the <i>current input character</i>.
<dt><i>name-start character</i>
<dd>
Switch to the <i>identifier state</i>.
Reconsume the <i>current input character</i>.
<dt>EOF
<dd>
Emit an end-of-file token.
<dt>anything else
<dd>
Emit a delim token
with its value set to the <i>current input character</i>.
Remain in this state.
</dl>
<h4>
<dfn>Double-quote-string state</dfn></h4>
<p>
If a string token has not yet been created since entering this state,
create a string token
with its value initially set to the empty string.
<p>
Consume the <i>next input character</i>.
<dl>
<dt>U+0022 QUOTATION MARK (")
<dd>
Emit the string token.
Return to the <i>data state</i>.
<dt>EOF
<dd>
This is a <i>parse error</i>.
Emit the string token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<dt><i>newline</i>
<dd>
This is a <i>parse error</i>.
Emit a bad-string token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i>
is an EOF,
this is a <i>parse error</i>.
Emit a bad-string token,
then switch to the <i>data state</i>.
<p>
Otherwise,
if the <i>next input character</i> is
a <i>newline</i>,
consume it.
Remain in this state.
<p>
Otherwise,
<i>consume an escaped character</i>.
Append the returned character to the string token's value.
Remain in this state.
<dt>anything else
<dd>
Append the <i>current input character</i>
to the string token's value.
Remain in this state.
</dl>
<h4>
<dfn>Single-quote-string state</dfn></h4>
<p>
If a string token has not yet been created since entering this state,
create a string token
with its value initially set to the empty string.
<p>
Consume the <i>next input character</i>.
<dl>
<dt>U+0027 APOSTROPHE (')
<dd>
Emit the string token.
Return to the <i>data state</i>.
<dt>EOF
<dd>
This is a <i>parse error</i>.
Emit the string token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<dt><i>newline</i>
<dd>
This is a <i>parse error</i>.
Emit a bad-string token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i>
is an EOF,
this is a <i>parse error</i>.
Emit a bad-string token,
then switch to the <i>data state</i>.
<p>
Otherwise,
if the <i>next input character</i> is
a <i>newline</i>,
consume it.
Remain in this state.
<p>
Otherwise,
<i>consume an escaped character</i>.
Append the returned character to the string token's value.
Remain in this state.
<dt>anything else
<dd>
Append the <i>current input character</i>
to the string token's value.
Remain in this state.
</dl>
<h4>
<dfn>Hash state</dfn></h4>
<p>
Consume the <i>next input character</i>.
<dl>
<dt><i>name character</i>
<dd>
Create a hash token
with its value set to the <i>current input character</i>.
Switch to the <i>hash-rest state</i>.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i> is
a <i>newline</i> or EOF,
emit a delim token
with its value set to U+0023 NUMBER SIGN (#).
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
<i>consume an escaped character</i>.
Create a hash token
with its value set to the returned character.
Switch to the <i>hash-rest state</i>.
<dt>anything else
<dd>
Emit a delim token
with its value set to U+0023 NUMBER SIGN (#).
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
</dl>
<h4>
<dfn>Hash-rest state</dfn></h4>
<p>
Consume the <i>next input character</i>.
<dl>
<dt><i>name character</i>
<dd>
Append the <i>current input character</i>
to the hash token's value.
Remain in this state.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i> is
a <i>newline</i> or EOF,
emit the hash token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
<i>consume an escaped character</i>.
Append the returned character to the hash token's value.
Remain in this state.
<dt>anything else
<dd>
Emit the hash token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
</dl>
<h4>
<dfn>Comment state</dfn></h4>
<p>
Consume the <i>next input character</i>.
<dl>
<dt>U+002A ASTERISK (*)
<dd>
If the <i>next input character</i> is
U+002F SOLIDUS (/),
consume it,
emit a comment token,
and switch to the <i>data state</i>.
<p>
Otherwise,
do nothing
and remain in this state.
<dt>EOF
<dd>
This is a <i>parse error</i>.
Emit a comment token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<dt>anything else
<dd>
Do nothing
and remain in this state.
</dl>
<h4>
<dfn>At-keyword state</dfn></h4>
<p>
Consume the <i>next input character</i>.
<dl>
<dt>U+002D HYPHEN-MINUS (-)
<dd>
If the <i>next input character</i> is a <i>name-start character</i>,
consume it.
Create an at-keyword token
with its value set to U+002D HYPHEN-MINUS
followed by the <i>current input character</i>.
Switch to the <i>at-keyword-rest state</i>.
<p>
Otherwise,
emit a delim token
with its value set to U+0040 COMMERCIAL AT (@).
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<dt><i>name-start character</i>
<dd>
Create an at-keyword token
with its value set to the <i>current input character</i>.
Switch to the <i>at-keyword-rest state</i>.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i> is
a <i>newline</i> or EOF,
emit a delim token
with its value set to U+0040 COMMERCIAL AT (@).
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
<i>consume an escaped character</i>.
Create an at-keyword token
with its value set to the returned character.
Switch to the <i>at-keyword-rest state</i>.
<dt>anything else
<dd>
Emit a delim token
with its value set to U+0040 COMMERCIAL AT (@).
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
</dl>
<h4>
<dfn>At-keyword-rest state</dfn></h4>
<p>
Consume the <i>next input character</i>.
<dl>
<dt><i>name character</i>
<dd>
Append the <i>current input character</i>
to the at-keyword token's value.
Remain in this state.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the <i>next input character</i> is
a <i>newline</i> or EOF,
emit the at-keyword token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
<p>
Otherwise,
<i>consume an escaped character</i>.
Append the returned character to the at-keyword token's value.
Remain in this state.
<dt>anything else
<dd>
Emit the at-keyword token.
Switch to the <i>data state</i>.
Reconsume the <i>current input character</i>.
</dl>
<h4>
<dfn>Identifier state</dfn></h4>
<p>
Consume the <i>next input character</i>.