Author: Althaf M Ahmed

Page Rank was developed at Stanford University California and patented by the United States Patent in 1998 as a Method for Node Ranking in a Linked Data Base assigned to The Board of Trustees of the Leland Stanford Junior University. Its name comes from its developer Larry Page, with whom later Sergey Brin joined in research for a new search engine. Their project started in 1995 and in 1998 the two developers of Page Rank founded Google Inc. Page Rank is nowadays a trademark of Google and provides the basis for Google's web search.

Google uses Page Rank in order to determine the importance or relevance a website has. As Google itself describes it, this method relies on the link structure between different web pages and interprets a link from page A to page B as a vote made by page A for page B.

Not only the number of votes is relevant, but also the page that makes the vote is quoted and therefore its vote is more or less important. Page Rank assigns, by using this method, each web page a value from 1 to 10. The Page Rank scale is logarithmic just like the Richter-Scale.

The algorithm is something like this in the case of four web pages A, B, C and D. If pages B, C and D all link to A, than the Page Rank assumed to A can be calculated like this PR(A) = PR(B) + PR(C) + PR(D).

However pages B, C and D can include also links to other web pages than A. If we call L(X) the number of outbound links on a site X than PR(A) = PR(B)/L(B) + PR(C)/L(C) + PR(D)/L(D). The algorithm also includes a damping factor, which should cover the probability of a surfer stooping clicking on links.

However it is clear that a web site's Page Rank derives from those other web pages which link to it. In order to do this calculus as quick and as reliable as possible a matrix and a vector are introduced.

The Page Rank algorithm may be very smart, but it is also utterly vulnerable. Many academic papers have been published to help improve Page Rank in order for it to ignore documents with falsely inflated Page Rank.

There have been also developed alternatives to this algorithm, like the HITS algorithm, Trust Rank and the CLEVER project. The most common type of manipulation is the so called 302 Google Jacking, which takes advantage of the fact that any web page redirected through a 302 server header or by a "refresh" meta-tag to a web page with a higher Page Rank acquires the higher Page Rank.

There are also companies selling Page Ranks to webmasters and as pages with higher Page Ranks are believed to be more valuable, they are also more expensive. In order to avoid such pages having a higher PR than they deserve, pages with an unusually high PR are checked regularly.

As mentioned before Google is constantly improving Page Rank. At the beginning of 2005 a new value has been introduced for the rel-attribute of HTML link and anchor elements, namely the "nofollow" value.

This value is useful to bloggers and web site builders who do not want the links on their pages to be evaluated by Page Rank in order to avoid Page Rank being affected by these. There is also the Google Toolbar which displays the Page Rank if you have it installed on your browser.

Another way of finding out the Page Rank of a specific page or domain is by visiting links like www.checkpagerank.com.

Google's search business is also explained in "The Google Story - Inside the Hottest Business, Media and Technology of our Time" by David A. Vise and Mark Malseed.

About the Author:
Althaf Ahmed is the owner of Imc2003.com, a Blog related to earn a living off the Internet. Mr. Althaf shares his knowledge that he has gained from his 5 years of online experience. Visit http://www.imc2003.com Today!

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