[css-grid-1] Better subheadings.

Author: fantasai

css-grid-1/Overview.bs

@@ -1424,7 +1424,10 @@ Explicit Track Sizing: the 'grid-template-rows' and 'grid-template-columns' prop
 		<dfn>&lt;line-names></dfn>          = '[' <<custom-ident>>* ']'
 	</pre>
 
-	Where:
+	Where the component values are defined as follows&hellip;
+
+<h4 id="track-sizes">
+Track Sizes</h4>
 
 	<dl dfn-for="grid-template-columns, grid-template-rows" dfn-type=value>
 		<dt><dfn><<length-percentage>></dfn>
@@ -1580,7 +1583,7 @@ Explicit Track Sizing: the 'grid-template-rows' and 'grid-template-columns' prop
 -->
 
 <h4 id='named-lines'>
-Named Grid Lines: the <css>[<<custom-ident>>*]</css> syntax</h4>
+Naming Grid Lines: the <css>[<<custom-ident>>*]</css> syntax</h4>
 
 	While <a>grid lines</a> can always be referred to by their numerical index,
 	<dfn export lt="named line">named lines</dfn>
@@ -1835,7 +1838,7 @@ Flexible Lengths: the ''fr'' unit</h4>
 -->
 
 <h4 id='computed-tracks'>
-Computed Values</h4>
+Computed Value of a Track Listing</h4>
 
 	A <dfn>computed track list</dfn> is a <a spec=infra>list</a>
 	alternating between [=line name sets=] and [=track sections=],
@@ -1863,7 +1866,7 @@ Computed Values</h4>
 -->
 
 <h4 id='resolved-track-list'>
-Resolved Values</h4>
+Resolved Value of a Track Listing</h4>
 
 	The 'grid-template-rows' and 'grid-template-columns' properties are
 	<a>resolved value special case properties</a>. [[!CSSOM]]