I have been working as a web research analyst for 5 years now. As my profession demands, I have used Yahoo and Google extensively. Here whenever I have typed five keywords, only pages that contain all five keywords have been displayed in the results listing. It seems the new search engine on the web, accoona.com employs some sort of an artificial intelligence software which looks at the context of the search - not just the keywords - because it throws up much more relevant results.