CSS is an abbreviation.
Its stands for Cascading Style Sheets.
When css are used in a website,css hold the rules about the overall presentation of the content.
Css was developed in 1997 by the World Wide Consortium(W3c) but only really became popular in the year 2000. Any webpage that is written in a markup language such as XHtml,Xml can use css. Most all browsers today support css.
When css defines how elements are to be displayed on a website the styles on each webpage can be updated more easily because only one file usually have to be updated to change the all the webpage on the website that use that css file.
Css cover background images, fonts, width, height, positions of elements and a lot more on the website.Css can also be used for other media , example: css can create a print style,css can define how a webpage is printed out. Navigation, images, and change colors to black on white can be removed from the webpage when a webpage is printed.