[css-multicol] fixing some code highlighting issues

Author: rachelandrew

css-multicol/Overview.bs

@@ -6,7 +6,7 @@ Level: 1
 Status: ED
 Work Status: Testing
 ED: https://drafts.csswg.org/css-multicol/
-TR: https://www.w3.org/TR/css3-multicol/
+TR: https://www.w3.org/TR/css-multicol-1/
 Previous Version: https://www.w3.org/TR/2011/CR-css3-multicol-20110412/
 Previous Version: https://www.w3.org/TR/2009/CR-css3-multicol-20091217/
 Previous Version: https://www.w3.org/TR/2009/WD-css3-multicol-20090630/
@@ -355,7 +355,7 @@ The multi-column model</h2>
 	<div class=example>
 		In this example, the width of the image is set with these rules:
 
-		<pre class=css>
+		<pre highlight="css">
 		img { display: block; width: 100% }
 		</pre>
 
@@ -411,7 +411,7 @@ The multi-column model</h2>
 	<div class="example">
 		In this example, this CSS fragment describes the presentation of the image:
 
-		<pre class="css">
+		<pre highlight="css">
 		img { display: block; float: right }
 		</pre>
 
@@ -973,7 +973,7 @@ Spanning columns</h2>
 		In this example, an <code>h2</code> element has been added to the
 		sample document after the sixth sentence (i.e., after the word "jkl."). This styling applies:
 
-		<pre class="css">
+		<pre highlight="css">
 		h2 { column-span: all; background: silver }
 		</pre>