non era difficilissimo cercare sul sito W3C
http://www.w3.org/Consortium/Legal/logo-usage-20000308

Frequently Asked Questions about Logos
Q1: Can I change a W3C logo to fit the look and feel of my site?

I'd like to use one of the W3C validator logos, but it doesn't match the design of my Web site. Can I change the logo?

No. The W3C Logo provides the organization with its visual identity. As a result, there are strict rules for its use. Changing the W3C logos is not permitted, as it defeats the purpose of the logo, which is to be noticed and identified as W3C.