It seems web development is running around in circles. A few years back, web development was a pain in the ... somewhere. Standards were upcoming as well as support, but the world simply was IE6 and there was no way around it.
Now lately this barrier is in the process of being broken. Microsoft is losing ground, and fast. The other browsers do support these new technologies so one might think the problem is solved... Wrong!
Right now there are 5 major players in the desktop browser scene. Two of them share the same rendering engine. Internet Explorer, Firefox, Chrome, Safari and Opera. And while IE still reigns (when combining all versions), it's reign is declining fast. It's last browser (IE8) is already behind Firefox' last version (Fx3.6).
With these browsers come new problems. Were you only forced to bend the rules for one browser in the past, now you're supposed to bend the rules for four of them. With webkit (Chrome/Safari) supporting more and more CSS3 features, other browsers are dropping behind. But the webkit browsers don't have a majority market share (by far) so those features can't really be used, since they clash with fallbacks.
This is especially problematic with HTML and CSS. There's no way of "preventing" fallback in case the browser does support some feature. So you have a choice; either support the newest feats and tell users of other browsers to ... go away. Or you can implement it the old way and leave the new features for personal projects...
This problem is actually forked and doubled by the mobile scene. Not only does it have to start from scratch, with browser wars starting all over again (on a much harder scale too), there's a zillion vendors competing for a piece of the pie now.
The Internet is evolving, and this is a good thing. But it will probably be a long time before we won't have to test one website in multiple browsers. Even longer for mobiles. And don't even get me started on tablets. Please. Don't.
This can be a bit frustrating at times. HTML5 is here, live and kicking. Ok, technically it's still being born, but we're using it. It's there and it pushed XHTML away. So I want to use it... While displaying it "unstyled" (without css) is not a big problem, using CSS is. The new tags cannot be styled "out-of-the-box".
I'm looking forward to using HTML5 and CSS3, but I'm afraid it'll take at least a year or so to finish the spec and about two more years to be able to safely use them, depending on how well IE9 will support it... (Goody, another IE to take into account!)