NegativeGrid fluid CSS grid by Chris Planeta

This is the description Chris gives his fluid CSS grid:
NegativeGrid is a lightweight, fluid CSS grid. I originally made it for myself but it turned out to be so good that Im publishing it here, for everybody to download. It is very compact and due to only three classes that you have to remember it is super-easy to learn. You can use it with media queries and is perfect for mobile-first approach.
NegativeGrid - fluid CSS grid by Chris Planeta