Respond.js
Respond.js is a fast & lightweight polyfill for min/max-width CSS3 Media Queries (for IE 6-8, and more). The goal of this script is to provide a fast and lightweight (3kb minified / 1kb gzipped) script to enable responsive web designs in browsers that don’t support CSS3 Media Queries – in particular, Internet Explorer 8 and under. It’s written in such a way that it will probably patch support for other non-supporting browsers as well.