Speaking of IE..... I think even the most apologist of Microsoft lovers (you know who you are!) who haven't already stopped reading this post will agree that IE6 was a horrible browser and anyone using it should upgrade to at least IE7 and optimally IE8, if for no reason other than the safety of their browsing and the overall experience you get on the web with a modern browser. The IE6 No More campaign is a set of code to insert on your pages that will display a nice message telling them that their browser is outdated and giving them a list of alternatives to download.
The issue with this is twofold though. On one hand, I hate pages that dictate what I can see or not see based on my browser (IE only sites that look just fine on Firefox anyone?) or IP/location (hello hulu). I surf some sites in elinks from a terminal session and if all I got was a "hey, you need a real browser" when I went there I'd go ballistic.
Secondly the longer IE6 is around, the longer web designers need to support it using up their valuable time, putting in hacks, or writing sites to the lowest common denominator. The idea of standards are there so that you can write something once and know that it'll look and work the same on all the browsers that users visit your site with.
Since this is just a strip of code inserted, nothing prevents the user from seeing the rest of the site, so it might not be that bad to pepper it to a few of your sites.