With no doubt, Internet in general ant the Web in particular have an increasing influence in our lives, and they have become a mass media and a first class information resource. The huge amount of information available in the Web is primary accessible to its users via search engines like Google, Yahoo! or Altavista. The companies operating these search engines are now multinational corporations with enormous financial incomes generated by their user traffic. But they will only survive if they keep being more and more useful for their users, something they can only achieve by innovating and implementing increasingly advanced technoloand fraud detection and control in search engines.