What is PageRank and How is it Calculated?
Web designers can think of Google PageRank as a reputation system, commonly used in many forums to indicate how many useful posts a user has made. It's a value that the Google search engine uses to calculate the importance of any given web page found in its index. Though Google has not disclosed the exact calculations used to assign PageRank, they have given web masters enough information that a simple model can be used to describe PageRank calculation.
For this simplified example, Page A, B and C each have assigned 30 points of reputation. If Page A links to Page B and Page C, the 30 points of reputation from Page A are evenly divided amongst Page B and Page C and added to their respective reputations. Page B and Page C each total 45 points of reputation with the links from Page A.
How Nofollow Links Were Being Used and Abused
The nofollow link was originally meant to give web designers a tool to combat the spammers that plagued blogs and forums of more legitimate web sites. This gave Page A the ability to tell search engines that it did not wish to vote for Page C's reputation.
However, an unintended side effect of the nofollow attribute allowed web designers to use the nofollow link to control the flow of PageRank within their own websites. If a web designer wanted only certain pages to rank highly in search engines, he would funnel all PageRank from the web site into the desired pages by using nofollow links for all other links on his site. This prevented Google from indexing a lot of high quality content that users might be searching for.
Read on
* How to Get Free Quality Backlinks to a Website
* How to Get Dofollow Backlinks
* Nofollow Links Are Not Backlinks
According to a blog posted on June 15, 2009 by Google guru, Matt Cutts, in an effort to better serve its customers Google began indexing links that contained the rel=nofollow attribute in late 2008. No formal announcement was made of this change; Google assumed that webmasters would notice the changes and modify their sites accordingly.