Keyboard Navigation Code - XPathEvaluate - need help

Hi every one

I am trying to use crossFire http://tkm.s31.xrea.com/xul/crossfire.shtml 
for keyboard navigation in XUL screen with no sucess...
In HTML its working very good - recommended

The problem is in this code that from some reason don't work under XUL 
files.

var path = '//a[@href] | //select |  //button | //input[not(@type="hidden")] 
| //textarea';

var resolver = doc.createNSResolver(doc.documentElement);

var xpathResult = doc.evaluate(path, doc.documentElement, resolver, 
XPathResult.ORDERED_NODE_ITERATOR_TYPE , null);

XpathResult returns nothing under XUL files, return all elements in HTML

What am I doing wrong here?

Thanks a lot

Adys.