In case you've been living in a cave recently, or don't read about web design much, the big news is that it is possible to run multiple versions of Internet Explorer on the same Windows box, side by side, just like any other application. Microsoft has claimed for a long time that IE was too integrated into the operating system for it to be a separate application, and web designers have struggled with how to test their sites in more than one version.
Turns out, there's been a secret back door ever since the IE3 days, something to do with an empty file called iexplore.exe.local. You can download simple zip files, unpack them in whatever directory you want, and run the iexplore.exe you find in them. You get a number of different IE versions running simultaneously. Some people are warning that in fact, you may not have precise fidelity with the actual versions, since there are bits and pieces pulled in at runtime from all over. That's probably true, but I tried the downloads, and sure enough, I got old browser behavior from the old ones and new behavior from the new ones, all at the same time.
So far, this month, I have had no visitors at all using IE3 (why would they!), but now at least I know what they would have seen.