Steps to re-occur browser warning:
<html>
<head>
<style>
/* IE header Warning css */
#ie-warning { line-height:37px; color:#fff; background-color: #e4042b; font:bold 14px arial; margin:0px auto; padding:8px 0 8px 0; text-align:center; }
#ie-warning a, #main-header #ie-warning a:visited{ color:#fff; text-decoration:underline; }
#ie-warning a:hover{ color:#fff; text-decoration:none; }
#ie-warning .warning-close { font-size:12px; cursor:pointer; }
</style>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('.warning-close').live('click', function () {
$(this).parent().fadeOut('fast', function () { $(this).remove(); });
document.cookie = "firsttime=1;path=/";
});
});
</script>
</head>
<body>
<?php
if (!isset($_COOKIE['firsttime']))
{ ?>
<!--[if IE]>
<div id="ie-warning">
This site is best viewed using <a target="_blank" href="http://www.mozilla.org/en-US/firefox/new/"> Firefox</a> and <a target="_blank" href="https://www.google.com/intl/en_uk/chrome/browser/"> Chrome</a>. <sup title="Close Warning" class="warning-close"> X </sup>
</div>
<![endif]-->
<?php } ?>
</body>
</html>