I once worked on a site that was aimed only at Mac users, and this was back in the pre-Chrome days when Safari was the browser that was really pushing the web forward with stuff like Canvas and CSS animations, so we made maximum use out of every bleeding-edge feature.
One day I figured I'd test it in IE just to see how broken it was (I can't remember if IE even had support for transparent PNG yet) and when I tested it, our site would literally crash IE. As massive Mac fanboys, we decided this was a feature.