Ensure long-hand background declaration usage for consistency.

Dominic Magnifico · Jonathan Neal · commit 5973b6a6e8ff · 2016-01-22T00:46:42.000-05:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 * Address inconsistent styling of b and strong.
 * Correct `hr` overflow in IE 8/9/10/11 and Edge 12.
+* Ensure `mark` long-hand background declaration usage.
 
 === 3.0.3 (March 30, 2015)
 
diff --git a/normalize.css b/normalize.css
@@ -149,7 +149,7 @@ h1 {
  */
 
 mark {
-  background: #ff0;
+  background-color: #ff0;
   color: #000;
 }
 
