Cascading Style Sheet
CSS or Cascading style sheet is the style sheet language of web, used to style or formatting of an HTML document.
Before we had CSS, all of the styling of HTML was embedded directly in the html document- like, attributes width or bgcolor (background color)
or in the form of presentational tags like font, center, strike etc.
Using separate style sheet for an entire site, a developer can apply styles across a whole site while updating a single css file.
Css was Developed by Hakon Wium Lie of MIT in 1995. In 1996, level 1 of CSS was published, level 2 comes in 1998 and level 3 ( CSS3) in 2009 with HTML5.
With HTML5, CSS has become the W3C standard for controlling visual presentation of web pages. W3C is celebrating 20th anniversary of css in 2016 as level 1 of css was published 20 years ago on 17 Dec 1996.