This is only a brief introduction to Cascading Style Sheets, but should give you a good starting point. And it includes pictures of fighting cats.
Slides
You can download a PDF version here.
Box model
For a details run down of all the implications of modelling boxes in this way, have a look at this article on CSS Tricks.
Sample website
You can download sample website files to play with - included are two html pages with some sample styles applied. Useful if you aren’t exactly sure where to start and just want to poke things around first.
Documentation
You’ve tried DocHub yesterday while looking up HTML tags and their attributes, but I find it evem more useful for looking up CSS properties.
Dabblet
Dabblet lets you deal with a small fragment of your site in separation from everything else. Includes lots of useful little touches: live preview as you type and tooltips that help you visualise the code.