[css-syntax] Clarify the note on the @charset "XXX"; byte sequence

Author: SimonSapin

css-syntax/Overview.html

@@ -4490,15 +4490,19 @@ <h3 class="heading settled heading" data-level=8.2 id=charset-rule><span class=s
 
 <p>	The <a class=css data-link-type=maybe href=#at-ruledef-charset title=@charset>@charset</a> rule has <strong>no effect on a stylesheet</strong>.
 
-<p class=note>	Note: However, the algorithm to <a data-link-type=dfn href=#determine-the-fallback-encoding title="determine the fallback encoding">determine the fallback encoding</a>
-	looks at the first several bytes of the stylesheet
-	to see if they’re a match for the ASCII characters <code>@charset "XXX";</code>,
-	where XXX is a sequence of bytes other than 22 (ASCII for <code>"</code>).
-	While this resembles an <a class=css data-link-type=maybe href=#at-ruledef-charset title=@charset>@charset</a> rule,
-	it’s not actually the same thing.
-	For example, the necessary sequence of bytes will spell out something entirely different
-	if the stylesheet is in an encoding that’s not ASCII-compatible,
-	such as UTF-16.
+	<div class=note>
+		Note: This only applies to the <a data-link-type=dfn href=#at-rule title=at-rule>at-rule</a>
+		created by the algorithm to <a data-link-type=dfn href=#parse-a-stylesheet0 title="parse a stylesheet">parse a stylesheet</a>,
+		not to the ASCII <code>@charset "XXX";</code> byte sequence
+		that the algorithm to <a data-link-type=dfn href=#determine-the-fallback-encoding title="determine the fallback encoding">determine the fallback encoding</a>
+		looks for at the beginning of a stylesheet.
+
+<p>		While they look similar, they are not actually the same thing.
+		For example, a slightly different byte sequence
+		(more whitespace, single instead of double quotes, …)
+		will not be considered for the fallback encoding
+		but may still generate an <a class=css data-link-type=maybe href=#at-ruledef-charset title=@charset>@charset</a> rule that shows up in <a data-biblio-type=informative data-link-type=biblio href=#cssom title=cssom>[CSSOM]</a>.
+	</div>
 
 
 

css-syntax/Overview.src.html

@@ -3016,15 +3016,19 @@ <h3 id='charset-rule'>
 
 	The ''@charset'' rule has <strong>no effect on a stylesheet</strong>.
 
-	Note: However, the algorithm to <a>determine the fallback encoding</a>
-	looks at the first several bytes of the stylesheet
-	to see if they're a match for the ASCII characters <code>@charset "XXX";</code>,
-	where XXX is a sequence of bytes other than 22 (ASCII for <code>"</code>).
-	While this resembles an ''@charset'' rule,
-	it's not actually the same thing.
-	For example, the necessary sequence of bytes will spell out something entirely different
-	if the stylesheet is in an encoding that's not ASCII-compatible,
-	such as UTF-16.
+	<div class='note'>
+		Note: This only applies to the <a>at-rule</a>
+		created by the algorithm to <a>parse a stylesheet</a>,
+		not to the ASCII <code>@charset "XXX";</code> byte sequence
+		that the algorithm to <a>determine the fallback encoding</a>
+		looks for at the beginning of a stylesheet.
+
+		While they look similar, they are not actually the same thing.
+		For example, a slightly different byte sequence
+		(more whitespace, single instead of double quotes, …)
+		will not be considered for the fallback encoding
+		but may still generate an ''@charset'' rule that shows up in [[CSSOM]].
+	</div>