Hi Everyone,
This is a free, web-development learning tool that may be useful to
you in learning CSS.
http://www.yoyobrain.com/subjects/show/471
If you "Add the subject to your learning drills," you can have the
site drill you on CSS concepts.
Our developers have found this method helpful in learning programming
languages. We're in the process of adding features to the site to
allow users to comment on existing content/build learning material
together/attribute content to various sources.
I hope you find it useful!
Best,
Elizabeth