CSS stands for "Cascading Style Sheets", and are used to control and manage font styles, font sizes, and web site color combinations that are used in a web page. In order to retain continuity of "look and feel" throughout a website, all pages within a website will often refer to a single CSS file. The CSS file is typically contained in a separate file from the website, and the various web pages retrieve the CSS file each time a web page is displayed. CSS files make global appearance changes easy -- a single change in a CSS file will mean that any pages using that CSS file will automatically display the changes.