The editable box model & color picker are very useful. I wonder if the editor would one day catch up so that you do your development in the browser itself.
I made my first contribution to Firefox the other day... I downloaded the source on a whim, realised I could build and run it - so went to the bug tracker.
There was a bug with the box model editor that if the labels were long (such as "auto") then they would overlap the borders. I made it so long labels will rotate 90 degrees (try it out, change the outside margin to "auto").
I'm pretty stoked that some code I wrote is in Firefox - seeing an advertised feature that I (in a small way) contributed to is pretty exciting!
