Tweak JS for omitting certain header elemenst from AnchorJS functiona…

…lity, add explanatory comments.

_pages/index.html

@@ -11,6 +11,10 @@
     <a class="a-skip-to-main" href="#main">Skip to main content</a>
     <header role="banner" class="site-header">
       <div class="wrapper">
+        <!-- This h1 element has this id because, unless we set it here,
+        kramdown will populate it with a value based on the content of the
+        element, which results in "18f-content-guide", which is an invalid 
+        value due to its starting with a numeral. -->
         <h1 id="title-18f-content-guide">{{site.title}}</h1>
         <p>{{site.description}}</p>
         {% jekyll_pages_api_search_interface %}

javascripts/application.js

@@ -114,10 +114,12 @@ $(document).ready(function() {
   // Add anchorJS anchors; see https://github.com/18F/content-guide/issues/149
   anchors.options.placement = 'right';
   anchors.add();
+  // Our logo is an h1 element but shouldn't have a visible anchor link:
   anchors.remove(".logo");
-  anchors.remove("#title-18f-content-guide");
-  anchors.remove("ol li h1");
-
+  // The header elements in the table of contents shouldn't have anchor links:
+  anchors.remove(".layout-table-of-contents h1")
+  // The page-title header elements shouldn't have anchor links:
+  anchors.remove(".page-title")
 });
 
 document.addEventListener('DOMContentLoaded', function() {