A useful resource?

I came across this and thought it might provide a useful resource, especially “The reference section includes a growing library of test cases for checking cross-browser and cross-platform compatibility.”

http://code.google.com/doctype/

I recently got stung by a cross-browser compatibility issue and had to roll back my changes (ouch!) so I’d be interested to know if/how anybody makes use of those test cases, as well as just the library in general.