Within a few minutes, I got stuck with the fact that I could not get any performance out of even a simple attempt at a CSS engine.
After about three days of mucking with that, I gave up on the project, and gained a lot more respect for Mozilla.
I did eventually get something that kind of worked, but that took about a day, and still suffered performance issues, probably because I had no idea what the hell I was doing (and still don't, really)
I never got around to implementing class support, but I did allow targeting an element via ID.
I did this in C++ for some reason, and used Xerces to parse the XML, and I used Allegro to render everything. If I were to try and make this now, I probably would not use a rendering system designed for games, but I was naive back then.
I'll have to look to see if I can find the old files on my NAS; if I can I'll put it on Github.