What is PageRank?

By CT Cheltenham

PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page's value.

In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyses the page that casts the vote.

Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important."

Important, high-quality sites receive a higher PageRank, which Google remembers each time it conducts a search. Of course, important pages mean nothing to you if they don't match your query. So, Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to your search.

Google goes far beyond the number of times a term appears on a page and examines all aspects of the page's content (and the content of the pages linking to it) to determine if it's a good match for your query.

Integrity:

Google's complex, automated methods make human tampering with their results extremely difficult. And although they do run relevant ads above and next to their results, Google does not sell placement within the results themselves (i.e., no one can buy a higher PageRank).

A Google search is an easy, honest and objective way to find high-quality web sites with information relevant to your search.

Google's PageRank Algorithm

Google's PageRank algorithm may look extremely complex if you're not a mathematician. However, in reality, its beauty lies in its simplicity!

PR(A) = (1-d) + d (PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))

PR(A) is the PageRank of a page

A PR(T1) is the PageRank of a page T1

C(T1) is the number of outgoing links from the page T1

d is a damping factor in the range 0 < d < 1, usually set to 0.85

PageRank is therefore calculated as a sum of the PageRanks of all the pages linking to it (inbound links), divided by the number of links on each of those pages (outbound links).

PageRank & Search Engine Optimisation

What does Google's PageRank algorithm tell us about Search Engine Optimisation?

Firstly it demonstrates that that the number of inbound liks to a web site is very important. However, more importantly it tells us that no inbound link can have a negative effect on a web sites PageRank!

Therefore, the worst thing an undesired inbound link can do is have no effect whatsoever on the PageRank of a web site / page.

Secondly the algorithm shows that the fewer outbound links on a single page providing an outbound link to a web site / page the better.

i.e. a link from a web page with only one outbound link is better than a a link from a web page with 10 outbound links on it.

Thirdly the algorithm demonstrates that it does not take into account any keywords / keyphrases whatsoever!

This is important as it shows that the algorithm itself is only part of the ranking process.