How Google Finds Your Needle in the Web's Haystack

Sometime back - when I searched for 'Prabath Siriwardena' in Google - my blog 'Memory Bank' did not appear in the search results - but after sometime it appeared in later pages of the search results - and even after sometime it became the top in the search results. When I searched for 'Prabath' in Google - my blog appeared in the second page of the search results - but when I did a search for 'Prabath' today - I saw it appearing in the first page as the second entry.

Following article explains how Google improves it's search results through page ranking : http://www.ams.org/featurecolumn/archive/pagerank.html. Since this involves little bit of Math and for those who hate to see mathematics equations - following summary will help.

Google's PageRank algorithm assesses the importance of web pages without human evaluation of the content. In fact, Google feels that the value of its service is largely in its ability to provide unbiased results to search queries; Google claims, "the heart of our software is PageRank." As we'll see, the trick is to ask the web itself to rank the importance of pages. The fundamental idea put forth by PageRank's creators, Sergey Brin and Lawrence Page, is this: the importance of a page is judged by the number of pages linking to it as well as their importance.

Each page is assigned a level of importance. For example, with a scale of 10, The American Mathematical Society currently has an importance of 8. That is 8/10. In other words the page rank of The American Mathematical Society is 8. So the question is how Google determines the page rank. How come The American Mathematical Society got a page rank of 8?

Take my blog as an example. In it I have links to Mahasen's blog and Chandana's blog. Say altogether I have 10 links in my blog to external web sites. Why I add those links to my site? The simple answer is they have some importance for me. So I am adding some importance to those sites and I need to pass some portion of the page rank of my site to those. In other words - say currently my site has a page rank of 2 - then I add 0.2 [that is 2/10 or (my page rank devided by the total number of links in my site to external sites] to Mahasen's site. But this does not mean that my page rank goes down - but it improves Mahasen's page rank.

Say if Amazon.com or CNN has a link to your site in their web sites - that will definitely improve the page rank of your site and will bring to the top of the search results.