Made some editorial edits based on a11y feedback.

Author: tabatkins

css3-images/Overview.html

@@ -922,8 +922,8 @@ <h3 id=element-reference><span class=secno>3.3. </span> Using Elements as
 #prev-preview { background: element(#prev-slide); }
 #next-preview { background: element(#next-slide); }
 &lt;/style>
-&lt;div id='prev-preview'>&lt;/div>
-&lt;div id='next-preview'>&lt;/div>
+&lt;a id='prev-preview'>Previous Slide&lt;/a>
+&lt;a id='next-preview'>Next Slide&lt;/a>
 &lt;section class='slide'>...&lt;/section>
 &lt;section class='slide current-slide'>...&lt;/section>
 ...</pre>

css3-images/Overview.src.html

@@ -472,8 +472,8 @@ <h3 id='element-reference'>
 #prev-preview { background: element(#prev-slide); }
 #next-preview { background: element(#next-slide); }
 &lt;/style>
-&lt;div id='prev-preview'>&lt;/div>
-&lt;div id='next-preview'>&lt;/div>
+&lt;a id='prev-preview'>Previous Slide&lt;/a>
+&lt;a id='next-preview'>Next Slide&lt;/a>
 &lt;section class='slide'>...&lt;/section>
 &lt;section class='slide current-slide'>...&lt;/section>
 ...</pre>