and I can just ignore IE6 users because these days you'd better keep your browser updated to the latest version for security reasons
...As if that would stop people.
I've seen a surprisingly large number of people that purposfully disabled the windows update simply because they doin't trust microsoft. There will a MANY people continueing to run IE6 for a long, long time. Heck, even IE 5.0 still has a market share of ~4% (*) which is almost twice as much as the percentage of people using Mozilla or Netscape.
IE 6.0 came out in 2001, and well over 5 years later IE5 is still alive and kicking.
More importantly: IE 7 *requires* XP servicepack 2, Vista, or windows 2003 server. It will NOT run on Win9x, ME, Windows 2000, or even a stock XP or XP-SP1. Especially including the latter two, that still encompasses a significant number of users.
(*) http://www.w3schools.com/browsers/browsers_stats.asp