This is time-consuming, plus you'll find lots of duplication. So, using a meta search engine saves time by searching several engines at once and by eliminating duplication. It even allows you to eliminate those that you don't want it to search. MetaCrawler does NOT search HotBot and many others, however. The second important thing to remember about meta search engines is that when you enter a complex search, there's no guarantee that every search engine queried will be able to understand the search you've entered.
Several factors influence relevancy ranking .
A search engines may give a web page a relevancy boost if it has a lot of links pointing to it or if it has been favorably reviewed. The location of a term within a Web site is also one of the factors upon which retrieval is ranked. For example, if you search for the phrase gene sequencing , sites with the phrase in the title or near the top of the page are assumed to be most relevant. Notice in the example below that the term gene sequencing appears at the top of the page. Relevancy ranking helps eliminate this sloppiness.