Heh, I happened to have had Opera set to identify itself as IE at the time I opened that page, so I was presented with your special message for IE6 users. =P
Adding to what I originally posted, I also sometimes check out
The Bunny System - Be warned, depicts much gratuitous violence being inflicted on squirrels. Written/drawn by someone I know.
As far as webcomics that I'm not currently reading because either I lost interest, the author stopped updating, the series was concluded, rarely updates, site went dead, or any other reason, there are quite a few. Some of them are:
Exploitation Now - Concluded
BoxJam's Doodles - Hasn't updated in a year, probably dead.
copper - tends to go months between updates
Demonology 101 - Concluded (I haven't gotten around to reading it to the end, though.)
Life of Riley - Having not checked on it in years, I find it's apparently dead and the site is now something unrelated, so the link goes to where a fan put up an archive.
Everything Jake - Ongoing, I fell out of it when I stopped reading webcomics for a while. Starts off just light college-life-humor-y, somewhere along the way it turns super-powery.
Elf Life - Apparently the original series completed and is now continued in some sort of follow-up or spin-off series. I recall it had some interesting plot ideas, but I stopped reading it years ago, during an annoying interminable side story arc about some fan-servicey siren and a thinly-disguised Popeye.
Corrupted Sprites - Elazul's sprite comic that doesn't seem to be up anymore; link is dead.
Eversummer Eve - Seems to still be ongoing. I barely remember this one because it's been a long time since I read it, but the story seems like it might be interesting and the art is great, so maybe I'll go back to it now.
One Small Step - Still ongoing, maybe I'll start following it again.
Perry Bible Fellowship - Some great "oh man that's just plain wrong" strips. Unfortunately, doesn't seem to be updated anymore.
Spamusement - Hillarious but no longer updated.
There are some others, but that's enough for now.