spamdexing

Spamdexing is any of various methods to manipulate the relevancy or prominence of resources indexed by a search engine, usually in a manner inconsistent with the purpose of the indexing system. It is a form of search engine optimization. Search engines use a variety of algorithms to determine relevancy ranking. Some of these include determining whether the search term appears in the META keywords tag, others whether the search term appears in the body text or URL of a web page. Many search engines check for instances of spamdexing and will remove suspect pages from their indexes.
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commercial Web sites want as many visits (hits) as possible. Some have attempted to increase their hit rate by fooling the search engines which hunt out and index sites into putting their pages near the top of lists produced in response to search queries. By burying many repetitions of key words within comments in their Web pages, they hope to fool search systems which rank sites by their relevance