Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 21651)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -540,6 +540,15 @@
 	display: inline-block;
 }
 
+/* Show navigation when JavaScript is off */ 
+.no-js .main-navigation ul.nav-menu,
+.no-js .main-navigation div.nav-menu > ul { 
+	display: block; 
+} 
+.no-js .menu-toggle { 
+	display: none; 
+} 
+
 /* Banner */
 section[role="banner"] {
 	margin-bottom: 48px;
Index: wp-content/themes/twentytwelve/functions.php
===================================================================
--- wp-content/themes/twentytwelve/functions.php	(revision 21651)
+++ wp-content/themes/twentytwelve/functions.php	(working copy)
@@ -376,6 +376,14 @@
 	elseif ( in_array( $background_color, array( 'fff', 'ffffff' ) ) )
 		$classes[] = 'custom-background-white';
 
+	/*
+	 * Provides support for JavaScript-disabled visitors,
+	 * allowing the menu to always show in small windows.
+	 *
+	 * Value is changed in navigation.js.
+	 */
+	$classes[] = 'no-js';
+
 	return $classes;
 }
 add_filter( 'body_class', 'twentytwelve_body_class' );
Index: wp-content/themes/twentytwelve/js/navigation.js
===================================================================
--- wp-content/themes/twentytwelve/js/navigation.js	(revision 21651)
+++ wp-content/themes/twentytwelve/js/navigation.js	(working copy)
@@ -4,10 +4,13 @@
  * Handles toggling the navigation menu for small screens.
  */
 ( function() {
+	// Remove no-js class from body.
+	document.body.className = document.body.className.replace( 'no-js', 'js' );
+
 	var button = document.getElementById( 'site-navigation' ).getElementsByTagName( 'h3' )[0],
 	    menu   = document.getElementById( 'site-navigation' ).getElementsByTagName( 'ul' )[0];
 
-	if ( undefined == button || undefined == menu )
+	if ( undefined === button || undefined === menu )
 		return false;
 
 	button.onclick = function() {