It was originally posted on the Quake3World level editing forums before the big f.u.b.a.r. of late 2004. Thanks to a forward thinking chap (thanks scourge34) a copy was saved and all was not lost..!
It's an ongoing resource that has been gathered over a number of years by several helpful and dedicated individuals from the Quake3World community and as the title suggests it's not a complete list of all the possible error messages that might crop up, but a comment on the more frequent problems that arise from editing and creating content for games based on the Quake 3 engine.