Cascading Style Sheets (CSS) is a style sheet language used for describing the look and formatting of a document written in a mark up language. CSS is designed primarily to enable the separation of document presentation, including elements such as the layout, colours, and fonts. This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple pages to share formatting, and reduce complexity and repetition in the structural content. It can also allow the same mark up page to be presented in different styles for different rendering methods, such as on-screen, in print, by voice and on tactile devices.           CSS can also be used to allow the web page to display differently depending on the screen size or device on which it is being viewed. CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element. In this so-called cascade, priorities or weights are calculated and assigned to rules, so that the results are predictable.