The cascading style sheet concept appeared in 1996 with the publication by W3C of a new recommendation entitled “CSS, Cascading Style Sheets”.

Cascading style sheets are created to compensate for the shortcomings of the HTML language for layout and presentation. They are useful when the house style of a site composed of several hundred web pages has to be changed – you can simply change the definition of the style sheets in a single location to change the appearance of the entire site!

The principle of cascading style sheets is to assign layout characteristics to a group of elements. For example, it is possible to decide to create a group of titles using a green, italic Arial font.

A name is used to define a layout characteristic, which is then called to apply it to a text, they are called cascading style sheets because several can be defined and, in the event of style redundancy, an order of priority is assigned by the browser.


Style sheets are used: 

• for uniform presentation throughout a site
• to change the appearance of the entire site by modifying a few lines
  
• improved legibility of HTML 
  
• rigorous positioning of elements 
  
• faster page loading
  

You can now link multiple CSS to the same website allowing your visitors to change font size, colors, backgrounds as they like.