Cascading Sheet Style File
CSS also known as Cascading Style Sheets are used in web documents and web pages for the addition of styles or formatting such as fonts, colour or spacing etc and because a whole web site can use the same CSS file it is possible to save space due to each page not needing to have its own CSS file. CSS is often used on sites that employ Dynamic HTML.
In 1996 CSS became a specification from the W3C or the World Wide Web Consortium in what was the level one specification, in 1998 the second level was released, the 3rd level specification uses modules instead of a single standard.
How to open .css files?
Software to open .css files
What are .css files