Mobile-First Responsive Web Design is a combination of philosophies/strategies, and ultimately boils down to a broader application of good ol' web bes
PIE makes Internet Explorer 6-9 capable of rendering several of the most useful CSS3 decoration features.
IE-CSS3 is a script to provide Internet Explorer support for some new styles available in the upcoming CSS3 standard.
This topic documents a feature of Visual Filters and Transitions, which is deprecated as of Windows Internet Explorer 9.
RGBa and ARGB interaction converter - RGBa for Internet Explorer
Use this page to see the differences in various box-shadow declarations across browsers.
In this web site I have collected various code samples and tests for CSS3.