Just to play Devil's Advocate a bit, but Safari is a royal pain to design properly for. Not that it's a bad browser but as far as the average web designer goes, there is no easy way from a Windows platform to test for it. Setting up a separate UNIX/Mac system with KHTML is one of those things that many designers may just avoid. A lot of designers ignore Opera for this reason as well, even if there is Win build of it.

Browser compatibility is at best irritating, but made even more so when there are no tools for your platform to test for a specific situation.

Standards! I thought we had these for a reason.