You can get some knowledge from http://www.w3schools.com about CSS and HTML. What'more, you can design your own site with Magic Theme - an awesome and responsive website designer with over 100 shortcodes instead of css and html.
More from: http://www.magictheme.com/
as hebby said w3 schools is a great site. You can also get a book on Amazon.com or eBay about web design, just read through it and don't worry IF you fail to understand it all on the first pass. Get a free website and just start playing.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them