CSS Backgrounds is a tutorial that will teach you how to use the CSS language to create and customize the background of a website. You will learn how to set a background color, add an image, create a gradient, and more. You will also learn how to use the various properties and
From Wikipedia
Cascading Style Sheets (CSS) is a style sheet language used for specifying the presentation and styling of a document written in a markup language, such as HTML or XML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.