[css-syntax] Add non-normative text to describe escaping.

Author: SimonSapin

css-syntax/Overview.html

@@ -66,7 +66,8 @@ <h2 class="no-num no-toc no-ref" id=contents><span class=content>Table of conten
 <div data-fill-with=table-of-contents><ul class=toc><li><a href=#intro><span class=secno>1</span>
 Introduction</a><ul class=toc><li><a href=#placement><span class=secno>1.1</span>
 Module interactions</a></ul><li><a href=#syntax-description><span class=secno>2</span>
-Description of CSS's Syntax</a><ul class=toc><li><a href=#error-handling><span class=secno>2.1</span>
+Description of CSS's Syntax</a><ul class=toc><li><a href=#escaping><span class=secno>2.1</span>
+Escaping</a><li><a href=#error-handling><span class=secno>2.2</span>
 Error Handling</a></ul><li><a href=#tokenizing-and-parsing-css><span class=secno>3</span>
 Tokenizing and Parsing CSS</a><ul class=toc><li><a href=#overview-of-the-parsing-model><span class=secno>3.1</span>
 Overview of the Parsing Model</a><li><a href=#the-input-byte-stream><span class=secno>3.2</span>
@@ -243,14 +244,41 @@ <h2 data-level=2 id=syntax-description><span class=secno>2 </span><span class=co
 	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.
+	by <a href=#escaping0>escaping</a> it.
 
 <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 &amp; Units spec</a>.
 	The special syntaxes of individual <a href=#at-rule>at-rules</a> can be found in the specs that define them.
 
+<h3 data-level=2.1 id=escaping><span class=secno>2.1 </span><span class=content>
+Escaping</span><a class=section-link href=#escaping>§</a></h3>
 
-<h3 data-level=2.1 id=error-handling><span class=secno>2.1 </span><span class=content>
+<p>	<em>This section is not normative.</em>
+
+<p>	Any Unicode character can be included in an identifier or quoted string
+	by <dfn data-dfn-type=link id=escaping0>escaping</dfn> it.
+	CSS escape sequences start with a backslash (\), and continue with:
+
+<p>	<ul>
+		<li>
+			Any Unicode character that is not a <a href=#hex-digit>hex digits</a> or a <a href=#newline>newline</a>.
+			The escape sequence is replaced by that character.
+		<li>
+			Or one to six <a href=#hex-digit>hex digits</a>, followed by an optional <a href=#whitespace>whitespace</a>.
+			The escape sequence is replaced by the Unicode character
+			whose codepoint number is given by the hexadecimal digits.
+			This optional whitespace allow hexadecimal escape sequences
+			to be followed by "real" hex digits.
+
+			<p class=example>
+				An identifier with the value "&amp;B"
+				could be written as <span class=css data-autolink=maybe>\26 B</span> or <span class=css data-autolink=maybe>\000026B</span>.
+
+			<p class=note>
+				A "real" space after the escape sequence must be doubled.
+	</ul>
+
+<h3 data-level=2.2 id=error-handling><span class=secno>2.2 </span><span class=content>
 Error Handling</span><a class=section-link href=#error-handling>§</a></h3>
 
 <p>	<em>This section is not normative.</em>

css-syntax/Overview.src.html

@@ -126,12 +126,39 @@ <h2 id='syntax-description'>
 	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.
+	by <a>escaping</a> it.
 
 	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 &amp; Units spec</a>.
 	The special syntaxes of individual <a>at-rules</a> can be found in the specs that define them.
 
+<h3>
+Escaping</h3>
+
+	<em>This section is not normative.</em>
+
+	Any Unicode character can be included in an identifier or quoted string
+	by <dfn>escaping</dfn> it.
+	CSS escape sequences start with a backslash (\), and continue with:
+
+	<ul>
+		<li>
+			Any Unicode character that is not a <a>hex digits</a> or a <a>newline</a>.
+			The escape sequence is replaced by that character.
+		<li>
+			Or one to six <a>hex digits</a>, followed by an optional <a>whitespace</a>.
+			The escape sequence is replaced by the Unicode character
+			whose codepoint number is given by the hexadecimal digits.
+			This optional whitespace allow hexadecimal escape sequences
+			to be followed by "real" hex digits.
+
+			<p class=example>
+				An identifier with the value "&B"
+				could be written as ''\26 B'' or ''\000026B''.
+
+			<p class=note>
+				A "real" space after the escape sequence must be doubled.
+	</ul>
 
 <h3>
 Error Handling</h3>