HTML5 Please : Look up HTML5, CSS3, etc features, know if they are ready for use, and if so find out how you should use them – with polyfills, fallbacks or as they
When can I use... : Compatibility tables for support of HTML5, CSS3, SVG and more in desktop and mobile browsers.
Selectivizr : CSS3 pseudo-class and attribute selectors for IE 6-8
Flexibility : Flexibility is a polyfill for Flexible Box Layout Module Level 1. Use it to design beautiful, flexible layouts on the web without sacrificing the expe...