how to design a nice website?

[Des]

Sites like Facebook, Twitter, Yahoo, etc all look top of the line. Obviously, they are the best sites on the web, but what I'm wondering is how they design their sites? Do they use just straight css and html5, or do they create it in Photoshop (or something of the sort) and slice the images up and use that? I've looked at their source code and it seems as though they mainly just use CSS/HTML5, but what do I know?
Thanks

[Ilove]

If you want nice theme check at http://mybb.com There are loads and loads of themes!

[kyle]

....

[Dan Filkovich]

Yeah I would say they just code the css/html. If you're good at coding css/html it is really easy to make simply good looking sites. Also, slicing in photoshop can be a huge pain for making dynamic websites.