CSS (Cascading Style Sheets) is a style language used for presenting information on the Web. There are two types of CSS, internal CSS (using tags) and external CSS (using the <link> element). While some people use internal CSS, the vast majority of web designers use external CSS, for its ability to change a whole web page by editing a few lines. See the Wikipedia article for in-depth information.

CSS Swatches
swatches | skins | tools | references
This is an abandoned wiki with few articles. As it is very important to the wikis focused on Web development, please consider editing it. The links page offers much useful material.