Cascading Style Sheets (CSS) are a powerful way to affect the presentation of a document or a collection of documents. Obviously, CSS is basically useless without a document of some sort, since it would have no content to present. Of course, the definition of "document" is extremely broad. For example, Mozilla and related browsers use CSS to affect the presentation of the browser chrome itself. Still, without the content of the chromebuttons, address inputs, dialog boxes, windows, and so onthere would be no need for CSS (or any other presentational information).