it allows you to create great-looking web pages. In the Introduction to HTML module we covered what HTML is, and how it is used to mark up documents. These documents will be readable in a web browser. Headings will look larger than regular text, paragraphs break onto a new line and have space between them. Links are colored and underlined to distinguish them from the rest of the text. What you are seeing is the browser’s default styles — very basic styles that the browser applies to HTML to make sure it will be basically readable even if no explicit styling is specified by the author of the page.
CSS can be used for very basic document text styling — for example changing the color and size of headings and links. It can be used to create layout — for example turning a single column of text into a layout with a main content area and a sidebar for related information. It can even be used for effects such as animation. Have a look at the links in this paragraph for specific examples.
body { color: red; }
h1 { color: #00ff00; }
p.ex { color: rgb(0,0,255); }