As far as design goes - Go on Behance and Dribble and copy other people's designs (but modify them and make them your own). You could try a book like hardboiled web design or designing for the web by Mark Boulton but it's best just to look at other people's designs and think about what it is you like about them.
As far as learning css - try books such as css master, css mastery, css in depth, css missing manual, css secrets or do an online thing like Treehouse or Rachel Andrews course. None of these resources will teach you to be a good designer though.