If you ever work with HTML, you are probably familiar with the stylesheet language known as Cascading Style Sheets (CSS). The purpose of CSS is to let you separate the presentation of a web page from the content. The content is described through a markup language such as HTML or XHTML. The presentation is managed through CSS.

Separating content from presentation makes the HTML cleaner and easier to read, and it also means that you can change the presentation across a whole site much more easily. Do you want to change all your h1 headers from centered blue 20-pt to left-aligned red 24-pt? With CSS, you can do that by changing a single file. CSS also improves accessibility; users with special needs can easily create custom style rules for easier access.

CSS Rules

Although it is possible to put CSS rules in an HTML file, it is better to create a separate CSS file, because it gives you a central point for managing the style. In a typical CSS scenario, the HTML header will look like that shown in Listing 1, and the CSS file will look like Listing 2.

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