“Grid-based layouts have become really popular among web designers over the last year… However, I ran into a problem when coding grid-based layouts. How can I be sure my grid is maintained from the original mockup to the final coded version? When I coded my first grid-based layout, I found myself regularly taking screenshots of the site and comparing them with my original grid in Photoshop. There had to be an easier way.
Enter GridFox. GridFox is a Firefox extension that overlays a grid on any website. If you can open it in Firefox, you can put a grid on top of it. It’s easy to customize, allowing you to create the exact grid you designed your layout around.”