Cascading Style Sheets (CSS) is a computer language used to describe the presentation of a structured document written in HTML, XHTML or XML. The CSS specification is maintained by the World Wide Web Consortium (W3C).
CSS is used to define colors, fonts, layout, and other aspects of document presentation. It is designed to separate document structure (written in HTML or a related language) from document presentation (written in CSS). This separation provides improved content accessibility and control in the of presentational characteristics. CSS is also capable of controlling the document's style separately in alternative rendering methods, such as on-screen, in print, by voice (when read out by a speech-based browser or screen reader) and on braille-based, tactile devices.