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How Search Engines Rank Web Pages
By Danny Sullivan, Editor (July 31, 2003)

When searching with crawler-based 
search engine, the search engine 
will matches the topic presented 
in the index.

The matches will be ranked, so that 
the most relevant ones come first.

How do crawler-based search engines 
determines relevancy?

They follow a set of rules, known as
an algorithm.

Exactly how a particular search engine's 
algorithm works is a closely-kept 
trade secret. 

However, all major search engines 
follow the general rules below.

  1. The location/frequency method.
    The main rules in a ranking algorithm involves the location and frequency of keywords on a web page.
    e.g. HTML title tag, top of a web page, higher frequency.

  2. Secret ingredients.
    search engines add their own secret ingredients to the location/frequency method. Nobody does it exactly the same which is why the same search on different search engines produces different results.
    e.g. some search engines index more web pages than others, some may also penalize pages or exclude them from the index.

  3. Off the page factors
    All major search engines now also make use of "off the page" ranking criteria. These factors are those that a webmasters cannot easily influence.

    Chief among these is link analysis (analyzing how pages link to each other).

    Another off the page factor is clickthrough measurement.


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