Or, just, y'know, use a reliable browser test (not sniffing the user-agent), and if you have an IE 6 user, then replace the page content with a gentle & friendly notice explaining that the site is not compatible with very old web browsers (this is something that a lot of users can understand), along with some helpful links to upgrading IE or downloading Firefox, and a link to a reliable webmaster contact at the bottom.
This is what I do, and it's had zero complaints so far -- on the one or two small sites I've done it for. ;-)
This is what I do, and it's had zero complaints so far -- on the one or two small sites I've done it for. ;-)