The Flexible Grid System is a 24-column responsive CSS grid system. It has an intuitive syntax and pretty decent browser support — it’ll even work as far back as IE 9.
Check out its demo page and resize your browser to see the demo web page layout reconfigure itself as you change the dimensions of your browser’s viewport.
If you’ve ever used the pioneer of web page layout grid systems, the 960 Grid System by Nathan Smith, at any point in your web design career then you’ll have no problems switching over to the Flexible Grid System, which shares a similar nomenclature and is clearly inspired by the former.
The Flexible Grid System is MIT-licensed. Get the latest version and view the source code of the system over at GitHub.