Fix csslint errors.

docs/examples/cover/cover.css

@@ -84,6 +84,7 @@ body {
 .masthead-nav > li > a:hover,
 .masthead-nav > li > a:focus {
   background-color: transparent;
+  border-bottom-color: #a9a9a9;
   border-bottom-color: rgba(255,255,255,.25);
 }
 .masthead-nav > .active > a,

docs/examples/sticky-footer-navbar/index.html

@@ -71,7 +71,7 @@
       <p>Back to <a href="../sticky-footer">the default sticky footer</a> minus the navbar.</p>
     </div>
 
-    <div id="footer">
+    <div class="footer">
       <div class="container">
         <p class="text-muted">Place sticky footer content here.</p>
       </div>

docs/examples/sticky-footer-navbar/sticky-footer-navbar.css

@@ -8,7 +8,7 @@ body {
   /* Margin bottom by footer height */
   margin-bottom: 60px;
 }
-#footer {
+.footer {
   position: absolute;
   bottom: 0;
   width: 100%;
@@ -29,7 +29,7 @@ body > .container {
   margin: 20px 0;
 }
 
-#footer > .container {
+.footer > .container {
   padding-right: 15px;
   padding-left: 15px;
 }

docs/examples/sticky-footer/index.html

@@ -37,7 +37,7 @@
       <p>Use <a href="../sticky-footer-navbar">the sticky footer with a fixed navbar</a> if need be, too.</p>
     </div>
 
-    <div id="footer">
+    <div class="footer">
       <div class="container">
         <p class="text-muted">Place sticky footer content here.</p>
       </div>

docs/examples/sticky-footer/sticky-footer.css

@@ -8,7 +8,7 @@ body {
   /* Margin bottom by footer height */
   margin-bottom: 60px;
 }
-#footer {
+.footer {
   position: absolute;
   bottom: 0;
   width: 100%;