PageRank
- PageRank
- Refers to Google's "PageRank" algorithm,
frequently abbreviated to PR. Google's PageRank algorithm
is used by the search engine to score pages based on the number of other pages
that link to it and is used to give an indication of the relative importance
of a page. Generally speaking pages with a higher page rank will be returned
before those with lower page ranks on the search engine's results page (cf
SERP). A high PageRank is therefore highly desirable.
The score assigned (or at least the score which is made visible to those outside of Google) is in the range 0 to 10, where 0 is very bad and 10 is extremely high (good). It has been suggested that:
- PageRank 0
- Often indicates that the page rank has not yet been assigned, or that the site has no inbound links.
- PageRank 1 to 2
- Very few inbound links, and those links are from low ranking sites.
- PageRank 3
- Site has some inbound links, either a large number of low quality links or a few links of good quality. Site will be returned on search results, but will tend to be outranked by other competitive sites.
- PageRank 4
- Site has many good inbound links. An achievable target for most small clubs and companies.
- PageRank 5
- Site has many good inbound links. Achievable with work. This is the highest PageRank that most sites can realistically aspire to.
- PageRank 6
- Very difficult to obtain because of the number and quality of inbound links required.
- PageRank 7-10
- Extremely difficult to obtain for all but the most popular websites. Often only obtained by websites that have become household names.
The original PageRank formula used and patented by Google was:
PR(A) = (1-d) + d(PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))where:
- PR(A)
- is the page rank of the page to be calculated.
- T1 ... Tn
- The pages which point to page A.
- d
- A damping factor, which can be set between 0 and 1 (typically 0.85) and which Google may set individually for sites.
- C(A)
- The number of links out from page A.
Google may have revised this formula since it was first introduced.
What the formula shows is that the page rank of a page will be higher the more pages link to it and that links from pages with a higher page rank count for more than links from pages with a lower page rank.
For more information see:
- http://toolbar.google.com/ - Download site for the Google toolbar. This is a toolbar for Internet Explorer and reveals the PageRank pages while surfing.
- http://infolab.stanford.edu/~backrub/google.html - The original paper where Sergey Brin and Lawrence Page presented the (initial) design of Google and first introduced and explained page rank.
- www.iwebtool.com/visual_pagerank - Page allows you to view a page, revealing the page rank of all of the links on the page.
- www.pagerank.dk/Pagerank-formula/Introduction.htm - Excellent introduction and explanation to the original PageRank formula used by Google.
- www.sirgroane.net/google-page-rank - Article explaining page rank.
- www.webrankinfo.com/english/pagerank - This article on Google PageRank, includes the original page rank formula first used by Google.
- http://everything.explained.at/pagerank - PageRank explained.
- http://pr.efactory.de - A survey of Google's PageRank algorithm. This contains a number of articles on the implications of PageRank.
- Effective SEO campaign includes quality link building services from high PageRank webpages.