I’ve used a debug css file for years. Its changed a lot over time but I seem to have settled on a format that works well with my workflow and other debugging tools (Firebug). This simple css file simply gives a background colour to every element to quickly enable me to see how well these elements are arranged on screen.
At a glance you can tell what’s not aligned correctly, where spacing is uneven and where certain elements are breaking out of their containers.

It’s nothing special but saves me a lot of time so I thought i’d share incase it helps anyone else out there.
Download: debug.css
Feel free to use and improve. Let me know how this could be made more useful.
November 9th, 2010 at 2:37 am
That works really nice, Rob! My own (slightly anal) opinion is to not use borders, but that’s because I like to see when things aren’t lining up without them.
Pretty darned good idea though!!
November 22nd, 2010 at 11:51 pm
Cheers Alex. It only changes the colour of existing borders to enable them to stand out more. The other lines you’ll see are outlines that wont effect the overall width of the box model.