[css-backgrounds-4] Fix grammar error.

Author: fantasai

css-backgrounds-4/Overview.bs

@@ -48,13 +48,13 @@ Background Positioning: the 'background-position' shorthand property</h3>
 	<pre class=prod><dfn><var>&lt;position&gt;</var></dfn> = [
 	  [ left | center | right | top | bottom | start | end | <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]
 	|
-	  [ left | center | right | start | end | <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]
-	  [ top | center | bottom | start | end | <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]
+	  [ left | center | right | x-start | x-end | <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]
+	  [ top | center | bottom | y-start | y-end | <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]
 	|
 	  [ center | [ left | right | x-start | x-end ] [ <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]? ] &amp;&amp;
 	  [ center | [ top | bottom | y-start | y-end ] [ <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]? ]
 	|
-	  [ center | [ start | end ] [ <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]? ] &amp;&amp;
+	  [ center | [ start | end ] [ <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]? ]
 	  [ center | [ start | end ] [ <var>&lt;percentage&gt;</var> | <var>&lt;length&gt;</var> ]? ]	]</pre>
 
 	Values have the following meanings:

css-backgrounds-4/Overview.html

@@ -316,13 +316,13 @@ <h3 class="heading settled" data-level="2.1" id="the-background-position"><span
 	</p>
    <pre class="prod"><dfn data-dfn-type="type" data-export="" id="typedef-position"><var>&lt;position></var><a class="self-link" href="#typedef-position"></a></dfn> = [  [ left <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> right <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> top <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> bottom <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> end <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]
 <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a>
-  [ left <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> right <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> end <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]
-  [ top <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> bottom <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> end <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]
+  [ left <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> right <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> x-start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> x-end <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]
+  [ top <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> bottom <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> y-start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> y-end <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]
 <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a>
   [ center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> [ left <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> right <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> x-start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> x-end ] [ <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]<a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a> ] &amp;&amp;
   [ center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> [ top <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> bottom <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> y-start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> y-end ] [ <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]<a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a> ]
 <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a>
-  [ center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> [ start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> end ] [ <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]<a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a> ] &amp;&amp;
+  [ center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> [ start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> end ] [ <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]<a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a> ]
   [ center <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> [ start <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> end ] [ <var>&lt;percentage></var> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one">|</a> <var>&lt;length></var> ]<a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a> ]  ]</pre>