A stylesheet language is a computer language used to describe the style of elements in a document marked up using a markup language. A modern one with widespread use is CSS (Cascading Style Sheets), which is used to documents like HTML, XHTML, SVG, and XUL.
Have you ever seen the guy that does intire web pages using CSS? Those are really nice. But I mostly use them for forums, wordpress, and my friends MySpace accounts.
CSS webpages are very nice to the eye. I personally know a handful of designers that stay strict to CSS webdesign and absolutely no other code for their layout.