I found the best way to learn CSS/HTML coding was to break it up into chunks. First I would try to learn how to style text, then images, then backgrounds and slowly work it up from there. It's a much more manageable way of learning.
Firebug (an extension for Firefox) is an invaluable tool, as it not only lets you look at the code of other websites, but you can also alter the code. This is an easy way to work out what certain CSS properties do.
However, before looking at other people's code, I would recommend using some beginners CSS/HTML tutorials and just learn the basics of styling text and images. Otherwise, you might find it hard to understand the code of other sites.
I found this site really useful when I was learning:
http://htmldog.com, but that was a couple of years ago, so I am not sure how good it is now.
It's worth remembering that good design does not come from Dreamwaver.
I'd recommend the book "The Non-Designer's Design Book" by Robin Williams. The book has very little to do with websites (although there is a web version available), but it explains four simple principles that will help aid any design. It only takes an hour to read at most and will dramatically improve your design skills.