What is PageRank?

PageRank is a numeric value that represents how important a page is on the web. Google figures that when one page links to another page, it is effectively casting a vote for the other page. The more votes that are cast for a page, the more important the page must be. Also, the importance of the page that is casting the vote determines how important the vote itself is. Google calculates a page`s importance from the votes cast for it. How important each vote is is taken into account when a page`s PageRank is calculated. PageRank is Google`s way of deciding a page`s importance. It matters because it is one of the factors that determines a page`s ranking in the search results. It isn`t the only factor that Google uses to rank pages, but it is an important one. PageRank is occasionally refer to as "PR".

Notes:
Not all links are counted by Google. For instance, they filter out links from known link farms. Some links can cause a site to be penalized by Google. They rightly figure that webmasters cannot control which sites link to their sites, but they can control which sites they link out to. For this reason, links into a site cannot harm the site, but links from a site can be harmful if they link to penalized sites. So be careful which sites you link to. If a site has PR0, it is usually a penalty, and it would be unwise to link to it.

How is PageRank calculated?

In simplest terms PR is calculated by the sharing of PR from all the IBL links to your page. This is not strictly accurate because Google also uses the internal links within a site in the calculation of PR. Each link to a page carries with it and passes PR value to the target page. The PR points or value passed depend on the PR value of the page they come from, and the total outbound links from the page. It is generally agreed that a page will only pass about 85% of its value to the page it links to. So a PR5 page with a single outbound link will pass 85% of the value of a PR5 page to the page it links to.

But virtually no page has only a single link -- remember internal links are also used in the total outbound link count -- so the value passed to any page is 85% of the PR, divided by the total number of outbound links.

The question now becomes what is the PR point value of the different PR levels. Most observers believe that the relationship between PR levels is logarithmic rather than linear. In other words PR5 is not worth 25% more than a PR4, but may be worth 4 to 6 times more.

It is also understood that a PR value is not a single number, but is in fact a range of values. So not all PR6 ranked pages are equal.