I was reminded of a campaign to persuade people to upgrade old browsers called Push Up the Web. This is a simple bit of JavaSript that detects what browser you’re using, and if it is ancient and decrepit (ie IE; Firefox2, Safari2, Opera9.5), then it pops up a window giving a download to the upgrade.
The question is though, what if you can’t upgrade? I worked at The Ministry of Magic a couple of years ago, and they were using Windows NT and IE5.5. Ow, old. Would you really want to be reminded of your backwardness? Would it not be punishment enough to be using IE5.5?