Index: wp-content/themes/twentytwelve/header.php
===================================================================
--- wp-content/themes/twentytwelve/header.php	(revision 28290)
+++ wp-content/themes/twentytwelve/header.php	(working copy)
@@ -40,7 +40,7 @@
 		</hgroup>
 
 		<nav id="site-navigation" class="main-navigation" role="navigation">
-			<h3 class="menu-toggle"><?php _e( 'Menu', 'twentytwelve' ); ?></h3>
+			<button class="menu-toggle"><?php _e( 'Menu', 'twentytwelve' ); ?></button>
 			<a class="assistive-text" href="#content" title="<?php esc_attr_e( 'Skip to content', 'twentytwelve' ); ?>"><?php _e( 'Skip to content', 'twentytwelve' ); ?></a>
 			<?php wp_nav_menu( array( 'theme_location' => 'primary', 'menu_class' => 'nav-menu' ) ); ?>
 		</nav><!-- #site-navigation -->
Index: wp-content/themes/twentytwelve/js/navigation.js
===================================================================
--- wp-content/themes/twentytwelve/js/navigation.js	(revision 28290)
+++ wp-content/themes/twentytwelve/js/navigation.js	(working copy)
@@ -8,7 +8,7 @@
 		return;
 	}
 
-	button = nav.getElementsByTagName( 'h3' )[0];
+	button = nav.getElementsByTagName( 'button' )[0];
 	menu   = nav.getElementsByTagName( 'ul' )[0];
 	if ( ! button ) {
 		return;
Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 28290)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -272,6 +272,7 @@
 	cursor: default;
 }
 .menu-toggle:hover,
+.menu-toggle:focus,
 button:hover,
 input[type="submit"]:hover,
 input[type="button"]:hover,