A specification for defining style, including text, graphics, and positioning of elements within a document. CSS version 1 is supported by virtually all web browsers and CSS version 2 by most recent ones.

CSS is a great web design time saver as it centralizes all style information in a document (color of headlines, for example) allowing far-reaching changes to be made by only editing the one associated CSS file. This concept also allows for different looks for the same document to be generated based on switching to a different CSS document - this can sometimes be done automatically (ie having one CSS for web viewing, another for printing)