HTML5 is a new technology and staying up-to-date with it sometimes might be pretty hard. Well, not anymore. HTML5 Please, an interactive compatibility chart of HTML5 and CSS3 features is here to help out.
Basically, using a smart search bar, you can filter trough results (browser/device support) and see what HTML5 or CSS3 elements or properties are supported in specific browser(s). Every item that you select is shortly described and also option on if they should be used with fallbacks or polyfills.
In short terms, if you need to check fast the support of a HTML5/CSS3 property or element, HTML5 Please is a must-bookmark website.