What is CSS?

CSS stands for 'Cascading Style Sheets' and it's these 'sheets' that are used alongside XHTML to produce the distinctive styling features on a web page. CSS can be very simple - for setting font colours, for example - or much more complex - positioning page elements precisely on screen, producing roll-over effects on links, and a lot more.

The beauty of using CSS is that because styling rules for a complete website are contained in a single place, usually a separate file that your browser refers to (although to complicate things they can be stored in a variety of different but complimentary places), making changes to a whole website is very easy to do - if you want, for instance, to change the size, colour and justification of a particular type of text across a 100 page website, you can do so once in the style sheet and every appropriate piece of text will change. Before the use of style sheets became widespread, every single text area would have needed to be changed individually, an onerous and time-consuming job.

Used together, XHTML and CSS are an efficient and powerful way to create the basic template around which a site can be developed.