May 8, 2009

SEO - Web site ranking: PageRank

Measuring your Website’s SEO quality is more than necessary. But what kind of tools and rankings are available? First, let’s see Google’s PR:

PageRank was developed at Stanford University by Larry Page (Lawrence originally, and hence the name Page-Rank) and later Sergey Brin. The key concept of PageRank is that a web page is generally more important, if many other web pages link to it. A page shares its PR with pages it links to.

PR(A) = (1-d) + d (PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))
  • PR(A) is the PageRank of page A,
  • PR(Ti) is the PageRank of pages Ti which link to page A,
  • C(Ti) is the number of outbound links on page Ti and
  • d is a damping factor which can be set between 0 and 1.
What is a damping factor?
The PageRank theory holds that even an imaginary surfer who is randomly clicking on links will eventually stop clicking. The probability, at any step, that the person will continue is a damping factor d. It is assumed that the damping factor will be set around 0.85.

where p1,p2,...,pN are the pages under consideration, M(pi) is the set of pages that link to pi, L(pj) is the number of outbound links on page pj, and N is the total number of pages.

How can we measure?