Designing Websites - What Browser to Code For?

flyingember asks: "I code up PHP/CSS webpages and recently wondered about who to code for. We know that each browser supports CSS a little bit differently than the others, likening back to the Netscape/Internet Explorer HTML wars. Opera or Mozilla hacks are seen constantly across the net. Looking through two years worth of saved webalizer statistics, 95% of my visits came from IE and the rest from Mozilla, these are the teeming masses of the internet. Even the traffic to my site two years ago resulting from this article sent 50% IE users on Windows XP, and the total was 95% from IE. The numbers have only grown more IE 6-dominant since then. Given the overwhelming Internet Explorer user base, unless your webpage is specifically targeting The *nix or Mac crowd why code for anything except IE 6?" While each browser does support CSS, and even some HTML a bit differently, what functionality seem to be universal across all of the major modern players? Can you design a sharp looking website with such features, without resorting to browser-specific code? If so, how?