Brilliant! Rated 5 out of 5 stars

Excellent piece of kit. Makes life much easier.
Only ever had one problem, and that turned out to be my fault for installing the windows version on a Mac (lol)
Superb addon that means that I can check what's valid without having to trek to the W3c website

This review is for a previous version of the add-on (0.8.4.0).