Assorted accessibility (and some consistency) fixes for documentation

Closes #14951 by merging it.

docs/examples/cover/index.html

@@ -38,11 +38,13 @@
           <div class="masthead clearfix">
             <div class="inner">
               <h3 class="masthead-brand">Cover</h3>
-              <ul class="nav masthead-nav">
-                <li class="active"><a href="#">Home</a></li>
-                <li><a href="#">Features</a></li>
-                <li><a href="#">Contact</a></li>
-              </ul>
+              <nav>
+                <ul class="nav masthead-nav">
+                  <li class="active"><a href="#">Home</a></li>
+                  <li><a href="#">Features</a></li>
+                  <li><a href="#">Contact</a></li>
+                </ul>
+              </nav>
             </div>
           </div>
 

docs/examples/dashboard/index.html

@@ -58,7 +58,7 @@
       <div class="row">
         <div class="col-sm-3 col-md-2 sidebar">
           <ul class="nav nav-sidebar">
-            <li class="active"><a href="#">Overview</a></li>
+            <li class="active"><a href="#">Overview <span class="sr-only">(current)</span></a></li>
             <li><a href="#">Reports</a></li>
             <li><a href="#">Analytics</a></li>
             <li><a href="#">Export</a></li>

docs/examples/jumbotron-narrow/index.html

@@ -31,11 +31,13 @@
 
     <div class="container">
       <div class="header">
-        <ul class="nav nav-pills pull-right" role="tablist">
-          <li role="presentation" class="active"><a href="#">Home</a></li>
-          <li role="presentation"><a href="#">About</a></li>
-          <li role="presentation"><a href="#">Contact</a></li>
-        </ul>
+        <nav>
+          <ul class="nav nav-pills pull-right">
+            <li role="presentation" class="active"><a href="#">Home</a></li>
+            <li role="presentation"><a href="#">About</a></li>
+            <li role="presentation"><a href="#">Contact</a></li>
+          </ul>
+        </nav>
         <h3 class="text-muted">Project name</h3>
       </div>
 

docs/examples/justified-nav/index.html

@@ -33,14 +33,16 @@
 
       <div class="masthead">
         <h3 class="text-muted">Project name</h3>
-        <ul class="nav nav-justified">
-          <li class="active"><a href="#">Home</a></li>
-          <li><a href="#">Projects</a></li>
-          <li><a href="#">Services</a></li>
-          <li><a href="#">Downloads</a></li>
-          <li><a href="#">About</a></li>
-          <li><a href="#">Contact</a></li>
-        </ul>
+        <div role="navigation">
+          <ul class="nav nav-justified">
+            <li class="active"><a href="#">Home</a></li>
+            <li><a href="#">Projects</a></li>
+            <li><a href="#">Services</a></li>
+            <li><a href="#">Downloads</a></li>
+            <li><a href="#">About</a></li>
+            <li><a href="#">Contact</a></li>
+          </ul>
+        </div>
       </div>
 
       <!-- Jumbotron -->

docs/examples/navbar-fixed-top/index.html

@@ -62,7 +62,7 @@
           <ul class="nav navbar-nav navbar-right">
             <li><a href="../navbar/">Default</a></li>
             <li><a href="../navbar-static-top/">Static top</a></li>
-            <li class="active"><a href="./">Fixed top</a></li>
+            <li class="active"><a href="./">Fixed top <span class="sr-only">(current)</span></a></li>
           </ul>
         </div><!--/.nav-collapse -->
       </div>

docs/examples/navbar-static-top/index.html

@@ -61,7 +61,7 @@
           </ul>
           <ul class="nav navbar-nav navbar-right">
             <li><a href="../navbar/">Default</a></li>
-            <li class="active"><a href="./">Static top</a></li>
+            <li class="active"><a href="./">Static top <span class="sr-only">(current)</span></a></li>
             <li><a href="../navbar-fixed-top/">Fixed top</a></li>
           </ul>
         </div><!--/.nav-collapse -->

docs/examples/navbar/index.html

@@ -45,9 +45,9 @@
           </div>
           <div id="navbar" class="navbar-collapse collapse">
             <ul class="nav navbar-nav">
-              <li class="active"><a href="#">Link</a></li>
-              <li><a href="#">Link</a></li>
-              <li><a href="#">Link</a></li>
+              <li class="active"><a href="#">Home</a></li>
+              <li><a href="#">About</a></li>
+              <li><a href="#">Contact</a></li>
               <li class="dropdown">
                 <a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <span class="caret"></span></a>
                 <ul class="dropdown-menu" role="menu">
@@ -62,7 +62,7 @@
               </li>
             </ul>
             <ul class="nav navbar-nav navbar-right">
-              <li class="active"><a href="./">Default</a></li>
+              <li class="active"><a href="./">Default <span class="sr-only">(current)</span></a></li>
               <li><a href="../navbar-static-top/">Static top</a></li>
               <li><a href="../navbar-fixed-top/">Fixed top</a></li>
             </ul>

docs/examples/signin/index.html

@@ -33,8 +33,10 @@
 
       <form class="form-signin" role="form">
         <h2 class="form-signin-heading">Please sign in</h2>
-        <input type="email" class="form-control" placeholder="Email address" required autofocus>
-        <input type="password" class="form-control" placeholder="Password" required>
+        <label for="inputEmail" class="sr-only">Email address</label>
+        <input type="email" id="inputEmail" class="form-control" placeholder="Email address" required autofocus>
+        <label for="inputPassword" class="sr-only">Email address</label>
+        <input type="password" id="inputPassword" class="form-control" placeholder="Password" required>
         <div class="checkbox">
           <label>
             <input type="checkbox" value="remember-me"> Remember me