[css-sizing-4] Fix markup. Editorial.

Author: tabatkins

css-sizing-4/Overview.bs

@@ -274,9 +274,9 @@ Intrinsic Aspect Ratios: the 'aspect-ratio' property</h3>
 			  height=315>
 		</pre>
 		<pre highlight="css">
-			@supports (aspect-ratio: attr(width) / 1) {
+			@supports (aspect-ratio: attr(width number) / 1) {
 			  iframe {
-			    aspect-ratio: attr(width) / attr(height);
+			    aspect-ratio: attr(width number) / attr(height number);
 			    width: 100%;
 			    height: auto;
 			  }
@@ -287,7 +287,7 @@ Intrinsic Aspect Ratios: the 'aspect-ratio' property</h3>
 	<div class="example">
 		In the following example:
 
-		<pre highlight=css>
+		<pre highlight=html>
 			&lt;div id=container style="height: 100px; float: left;">
 				&lt;div id=item style="height: 100%; aspect-ratio: 1/1;">content&lt;/div>
 			&lt;/div>
@@ -297,7 +297,7 @@ Intrinsic Aspect Ratios: the 'aspect-ratio' property</h3>
 		the width of the item resolves to 100px for both its intrinsic size contributions as well as for final layout,
 		so the container also sizes to a width of 100px.
 
-		<pre highlight=css>
+		<pre highlight=html>
 			&lt;div id=container style="height: auto; float: left;">
 				&lt;div id=item style="height: 100%; aspect-ratio: 1/1;">content&lt;/div>
 			&lt;/div>