Structure examples with appropriate <main>, <header>, <footer>

Structure examples with appropriate `<main>`, `<header>`, `<footer>`

docs/4.0/examples/cover/index.html

@@ -24,7 +24,7 @@
 
         <div class="cover-container">
 
-          <div class="masthead clearfix">
+          <header class="masthead clearfix">
             <div class="inner">
               <h3 class="masthead-brand">Cover</h3>
               <nav class="nav nav-masthead">
@@ -33,21 +33,21 @@
                 <a class="nav-link" href="#">Contact</a>
               </nav>
             </div>
-          </div>
+          </header>
 
-          <div class="inner cover">
+          <main role="main" class="inner cover">
             <h1 class="cover-heading">Cover your page.</h1>
             <p class="lead">Cover is a one-page template for building simple and beautiful home pages. Download, edit the text, and add your own fullscreen background photo to make it your own.</p>
             <p class="lead">
               <a href="#" class="btn btn-lg btn-secondary">Learn more</a>
             </p>
-          </div>
+          </main>
 
-          <div class="mastfoot">
+          <footer class="mastfoot">
             <div class="inner">
               <p>Cover template for <a href="https://getbootstrap.com">Bootstrap</a>, by <a href="https://twitter.com/mdo">@mdo</a>.</p>
             </div>
-          </div>
+          </footer>
 
         </div>