<html xmlns='http://www.w3.org/1999/xhtml'> 
<head> 
<title>msubsup javascript subscript change test</title> 
</head> 
<body> 
<p> 
<math xmlns='http://www.w3.org/1998/Math/MathML'> 
<msubsup id="subsup"><mi>x</mi><mn>1</mn><mi>k</mi></msubsup> 
</math> 
</p> 
<script type='text/javascript'>
var msubsup = document.getElementById("subsup");
msubsup.removeChild(msubsup.firstChild.nextSibling);
var sub = document.createElementNS("http://www.w3.org/1998/Math/MathML","mn");
sub.appendChild(document.createTextNode("2"));
msubsup.insertBefore(sub,msubsup.firstChild.nextSibling);
</script>
</body>
</html>