Bringing Modern CSS to Internet Explorer

http://selectivizr.com/

CSS3 selectors for IE

selectivizr is a JavaScript utility that emulates CSS3 pseudo-classes and attribute selectors in Internet Explorer 6-8. Simply include the script in your pages and selectivizr will do the rest.

http://css3pie.com

PIE makes Internet Explorer 6-8 capable of rendering several of the most useful CSS3 decoration features.

http://www.modernizr.com/

Modernizr adds classes to the element which allow you to target specific browser functionality in your stylesheet. You don't actually need to write any Javascript to use it.

Have you ever wanted to do if-statements in your CSS for the availability of cool features like border-radius? [...]

Modernizr is a small and simple JavaScript library that helps you take advantage of emerging web technologies (CSS3, HTML 5) while still maintaining a fine level of control over older browsers that may not yet support these new technologies.