HTML is how Web pages are structured. CSS is how Web pages are designed. This book deals primarily with how to use CSS to add a visual layer to the HTML structure of your Web pages. CSS is a style sheet language; that is, it is not a programming language. Instead, it’s code that tells a device (usually a Web browser) how the content in a file should be displayed. CSS is meant to be easily understood by anyone, not just “computer people.” Its syntax is straightforward, basically consisting of rules that tell an element on the screen how it should appear.