HTML5/CSS3 Which features you should and shouldn't use
Found this somewhat interesting and somewhat useful site. You can look up new features of HTML5 and CSS3 and see if they are features that are supported by a number of browsers/devices. Should you be using them now? It tells you if it's okay, good with fallbacks or polyfills or whether you should avoid using such features right now. Just a quick little reference tool. It seems as though it's still pretty new. I'm sure they'll continue adding information.