You had a running CSS engine within a day?
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.