Use Javascript strict mode

src/webui/www/public/login.html

@@ -8,6 +8,8 @@
     <link rel="stylesheet" type="text/css" href="css/login.css" />
     <script src="scripts/lib/mootools-1.2-core-yc.js"></script>
     <script>
+        'use strict';
+
         window.onload = function() {
             $('username').focus();
             $('username').select();