sorry i thought this is worldwide known
w3c is the World Wide Web Consortium. It is an international consortium where Member organizations, a full-time staff, and the public work together to develop Web standards for more see http://www.w3.org/Consortium/
The link i sended in the other document is the page where you can test, if the used html/xlm is valid w3c, and if not, what´s wrong
It took me a little while too, to get my notesdatabase to valid w3c see
http://www.asensys.de