How do search engines rank relevancy?

frequency of search term
§Frequency of keywords
§
§The result is that no search engine has the exact same collection (database) of web pages to search
§
§Search engines may also give a web page a relevancy
§ boost if it has a lot of links pointing to it or if it has been favorably reviewed
Search engines also rank relevancy by the frequency of a term in a site.  But beware:  people have caught on to this and "spam" their sites with terms in the hopes that their sites will be retrieved frequently.  This spamming is considered a violation of Netiquette, so most of the search engines "punish" sites that appear to have been spammed by not loading them in the search engine's database.

Legitimate frequency of a word or phrase is considered by a search engine, however.  For example, if you're looking for "witchcraft" the sites that are retrieved by a search should use that term frequently.

(DO A SEARCH IN HOTBOT FOR WITCHCRAFT.  LOOK AT THE FIRST SEVERAL HITS.  ALSO NOTE THAT HOTBOT HAS A FEATURE THAT RETRIEVES THE TOP TEN MOST FREQUENTLY VISITED SITES FOR EVERY SEARCH.)

http://witchcraft.simplenet.com/present.html