Todd Nienkerk of Four Kitchens explains the concept of CSS grid systems and gives some tips on how to get started with working with the 960 grid system. He talks a bit about the 960 Grid System Drupal theme as developed by dvessel, who was actually able to get some of his content-first innovations ported back into the 960 framework. He also briefly mentions the 960 Gridder module that sets up a javascript overlay to verify that your design is properly lining up. He talks about the general trends of CSS grids and some specific resources that help with getting started on creating a grid-based design.