Using Cascading Style Sheets, or CSS

Part of the Creating Web Pages All-in-One For Dummies Cheat Sheet

Cascading Style Sheets (CSS) is a styling language that enables you to create a more attractive, well-designed Web site and make it much easier to manage and organize. Here are three basic reasons that CSS is helpful when designing your Web site:

CSS gives you greater control over your page design. CSS has many formatting settings that HTML, by itself, does not provide. As a result, you can have much greater control over the look of your Web page by using CSS than just using normal HTML.
CSS allows you to separate your site content from the formatting instructions. The HTML document, therefore, becomes the place where you work with content, and the CSS style sheet serves as your place to set up your styles.
CSS enables you to manage styles across your site in one central location. Although you can define CSS styles inside a single Web page, its real power becomes evident when you use a separate CSS style sheet that every page in your Web site can access. When you set up your site like this, you can easily give your entire site a consistent look and feel. You can also make global changes from a single location.