I may be wrong but it seems to me Goodle, AOL and ASK's search results have similarities while Yahoo, MSN, Altavista, Lycos'... are different? What this mean to seo? Many thanks.
Well, it is not surprising. Google is shareholder of AOL. Google is provider of search results for AOL . (exclusive provider or not? I do not know). Google provides search results for other sites too. Similarly, Yahoo is shareholder of Overture and Altavista. The latter has abandoned ist search engine for several years and now uses Yahoo search results. Quite amazing because Altavista was an important search engine in the 1990's and was provider of Yahoo search at that time. BTW, In the early 2.000, yahoo search engine was powered by google . The partnership stopped in 2004 when yahoo (basically a portal and web directory) started with its own search engine.