Respond.js: Fast CSS3 Media Queries for Internet Explorer 6-8 and more
April 2020 note: Hi! Just a quick note to say that this post is pretty old, and might contain outdated advice or links. We're keeping it online, but recommend that you check newer posts to see if there's a better approach.
Mobile-first Responsive Web Design may just be the most practical and forward-looking way to address the multitudes of devices and browsers that reach your site. But lack of native CSS3 Media Query support in Internet Explorer 8 and under (among others) presents a serious challenge to the technique.
Filament Group’s own Scott Jehl has released a script to address the problem, and also achieves mobile-optimized filesize (3kb / 1kb gzipped) and near-native performance. You can learn more at the project site on Github: Respond.js Project (documentation here).