Hmm.. I just tried this and it worked for me:
Code:
<html>
<body>
<a href="#" onclick="Popup=window.open('test.txt','Popup','toolbar=no,location=no,status=no,menubar=no,scrollbars=yes,resizable=no, width=1000,height=300,'); return false;"> Test Window</a>
</body>
</html>
When I click the button it loads test.txt. I have changed the contents of test.txt and each time it loaded it without me doing a refresh or anything. Here's a working example:
http://www.peppermint-bay.com/test3.htm