For those more comfortable designing on a 24-column grid, an alternative version is available on the original website. It consists of columns 30 pixels wide, with 10 pixel gutters, and a 5 pixel buffer on each side of the container. This design keeps text from touching browser chrome. This can be helpful for devices like the iPhone, where a lower-case "i" or "l" might be easily missed.
By using the push_XX and pull_XX classes, elements can be rearranged, regardless of their order of apperance in the markup. By using these classes, more important info can be higher in the HTML, without sacrificing precision in your page layout.