<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<title>Testcase for bug </title>
<head>
<script type="text/javascript">
function boom() {
var colgroup = document.createElementNS("http://www.w3.org/1999/xhtml", 'colgroup');
document.getElementById('thead').insertBefore(colgroup, null);
}
</script>
<style type="text/css">
thead {border:3px solid purple;}
</style>
</head>
<body onload="boom()">
<table><thead id="thead"></thead></table>
</body>
</html>