Tune your site for Windows SP 2
I just upgraded to Service Pack 2 on my Windows XP Professional Box and when logged in back after a successful installation, suddenly the Flash Interface I was working on is no longer displayed. IE 6.0 told me that it had blocked the content (Active X) "to help protect your security, Internet Explorer has restricted this file from showing active content that could access your computer. Click here for options..."
Prepare yourself, read more about Upcoming Changes in Microsoft Windows XP Service Pack 2. View the recorded Breeze Presentation while it last.
Some of the must read articles on Microsoft are:
[Update: Thanks to JD for his comment about the issue, here is the relevant link.
The trick is to add <!-- saved from url=(0017)http://localhost/ --> on the second line of your html. Here, (0017) is the string length (http://localhost/) of your URL that follows it.]