The intention of WOT is that it is the users themselves who decide whether a site is safe or not, so that unlike other services such as SiteAdvisor that find dangerous websites, its database is continually updated.
WOT operation is very simple. When you perform any search on Google or Yahoo will see to the right of each result a ticket labeled green, yellow or red that tells you if the site is safe or not. The categories that WOT uses for this are Reliability, Loyalty seller privacy and safety for children, and you can give your score to the pages you visit at any time.
Moreover, if you agree that a page is not safe, WOT will show a warning if you go to it by a mistake.