Cascading Style Sheets (CSS) are a powerful way to affect the presentation of a document or a collection of documents. Obviously, without a document of some sort, CSS is basically useless 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 chrome buttons, address inputs, dialog boxes, windows, and so on there would be no need for CSS (or any other presentational information).