I have done my first pass at an IE6 warning element. I've decided to make a companion page to go along with it featuring download links to other browsers (this part isn't done yet). If I'm happy with the way it looks, I'll zip it up and let other people download it to add to their own sites. No javascript and no having to link to other sites. Though I think I'd like to have an optional cookie to allow visitors to hide the warning for a week or two, so that will need at least a couple of lines of JS.

If you have a copy of IE6 to test with, see the result here.

I'm also considering changing the image to a GIF instead of a PNG so that I can animate it scrolling down.