Javascript + XML +IE

[Gdwag]

What is needed to display XML data in javascript with IE

I have a normal responseXML with the following statement trying to popup the first value

var xmlDocument = http.responseXML;
var GoSize = xmlDocument.getElementsByTagName('go').item(0).firstChild.data;

This works fine in Firefox, but errors out in IE6.

What do I need to do to get this to work in IE???