Now we know the Maths behind PageRank calculation. PageRank is a way of Google of assigning importance to web pages, so that the high quality web sites get a higher pagerank. It still underlines the same thing – linking. More the number of links to a webpage, higher its pagerank. There is a lot of mathematics jargon, interesting for the interested, otherwise read the following excerpt.
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.
Here’s how the PageRank is determined. Suppose that page Pj has lj links. If one of those links is to page Pi, then Pj will pass on 1/lj of its importance to Pi. The importance ranking of Pi is then the sum of all the contributions made by pages linking to it.
However, David also mentions things like pagerank obtained elsewhere is in fact an approximation, Google never publishes the actual pagerank.
This can also be considered to be the reason behind all the spam. Spammers try to insert links to the target website so that its pagerank increases. I think, just like other metrics even the pagerank is just an indication of quality and can be manipulated. This algorithm assumes that linking will happen out of liking of a web site, but this can be manipulated using spamming and programs like link exchange. Scoble mentions how Microsoft can be world’s greatest SEO. Can there be a better algorithm for calculating and assigning importance to web pages?