This fix is deprecated and is no longer supported (meaning that I will not help you to get it working with your pages). It was only written to fill the gap while waiting for Internet Explorer to implement fixed positioning. That has now happened in IE 7. Although this fix can make it work in IE 6 as well, that is counter productive for the future of the Web. IE 6 is a major problem to Web developers (IE 7 is a problem as well, but for now, let's overlook that, since it does at least implement fixed positioning), and the sooner it stops being used, the better.
Instead of using this hack, users of IE 6 should be encouraged to upgrade to IE 7. Users who cannot upgrade to IE 7 (because IE 7 is not being released for most Windows operating systems) should use a better browser, such as Opera or Firefox. They have been abandoned by Microsoft.