A good introductory text is found at http://www.w3c.org/Style/Examples/011/firstcss

But very many similar sites are found around the world. The w3c is an organisation which has established standards for html and css. It can be quite usefull to see if a given stylesheet or web page in html follows these standards. The validators are found on the front page of w3c (http://www.w3c.org).

For epidata it is the intention to have all html and style sheets in compliance with the w3c standards. (Note intention - sometimes not accomplished)

regards Jens Lauritsen