[bgarbiak]

I deal with HTML and CSS everyday so I'm probably biased but for me all these cross-browser compatibility problems related to rendering stuff are grossly exaggerated. Aside from IE6 (which, I believe, should not be supported anymore) supporting everything else is relatively easy. IE7 usually needs a couple of "zoom: 100%" here and there; IE8 handles CSS2 quite nicely (it passed Acid 2 after all); IE9 is on the same level as Firefox 3.6 - which is quite great. CSS3 stuff is a bit tricky sometimes, especially if you're going for a pixel-perfect cross-browser compatibility. However, it's hard to expect that older browsers would support technology from the future. Flash 8 don't support Flash 11 features either. Still, in browsers the new stuff could be quite easily 'emulated' with filters, JS or ready-made solutions (PIE CSS), etc.

Latest Firefox, Opera, Safari, Chrome and IE10 - the bunch that supports both HTML5 and CSS3 from the start - are totally painless. That's the "HTML5 nirvana", IMHO. To be honest, breaking the compatibility between these the way the author did is quite an achievement - I really would like to see his code. Probably a quick and simple CSS Reset would solve these issues. Author's mistake is more probable though.