Since picking up RoR I have had to dig in to technologies which I had previously only glanced at. One of these is CSS, part of the DHTML set of technologies.
The experience has been rewarding and at times frustrating but the outcomes has been positive. It is a technology that people need to get their heads around in order to develop an effective and usable front end to your web application.
Here are some resources that eased the learning curve
The W3C CSS tutorial shouldn't be forgotten.
The same page offers some nifty overviews for colour selection, and a CSS reference (obviously).
The YUI Grid CSS ( http://developer.yahoo.com/yui/grids/ ) has become a standard include in all the RoR projects I do these days.
Simply put, it brings convention over configuration to your layouts.
The Reset and Fonts components are useful too, but Grid allows to just stop worrying about all the positioning issues, in a way that's cross-browser compatible by design.
It takes a bit of getting used to, but no longer having to go grey trying to figure out incompatibilities makes it worthwhile.
Yes, I had to do the same thing. While I'm glad I learned CSS and some DHTML from a "professional development" standpoint, I still can't say I really enjoy it.
BTW, the online resource I've used most is HTML Dog.
If you happen to be on Mac OS X, don't miss to try CSSEdit by http://www.macrabbit.com/ - it's a real time-saver.
I am having trouble running a Css file in my .aspx web project