CSS – Cascading Style Sheets is a language used for relating the formatting of a document written in a markup language. Although most often used to set the pictorial style of web pages and user interfaces written in HTML and XHTML, the language can be useful to any XML document, including plain XML, SVG and XUL, and is appropriate to rendering in communication , or on other broadcasting . Along with HTML and JavaScript, CSS is a keystone technology used by most websites to design visually good looking webpages, end user interfaces for web applications, and end user interfaces for many mobile applications.