PR(A) is the probability that a random surfer is on page A. Thus in crude terms the definition of PageRank is: " The probability that a random person surfing the web would be on your website". In the formula above the probabilities in the brackets are the probabilities or PageRank of the pages linking to page A. PageRank by definition the is a meusure between 0 and 1. The Google Toolbar however show Pagrank as a measuere from 1-10. This is just to make it easily readible and dislpayable and by doing it this way Google actually hide the true PageRank of a Page. One thing also to note is that the 1-10 scale is fitted logmaritmicly. What this basically means is that a website with a PageRank of 6 does not have twice the PageRank of a page with PageRank 3. It will be more than that. I would guess the PageRank of a PR 6 site to be around 100 times more than the PR of as site that has a PageRank of 3. I will in a later post try and fit actual PageRank with the toolbar.
Now that we are more familiar with how PageRank works I would like to explain why linking outside your site does not adversly affect your sites PageRank. I am not going to do it mathematically, I am just going to cite a paragraph out of Wiki witch I believe is true.
"When calculating PageRank, pages with no outbound links are assumed to link out to all other pages in the collection. Their PageRank scores are therefore divided evenly among all other pages. In other words, to be fair with pages that are not sinks, these random transitions are added to all nodes in the Web, with a residual probability of usually d = 0.85, estimated from the frequency that an average surfer uses his or her browser's bookmark feature."
In the orange highlighted part of the quote we can see that PageRank flows regardles of whether you link to pages outside your site or not. In fact. If you don't link outside your site. The google bot assumes the your are linking to all pages on the Web. At first this seems like a harsh penalty but actually has a logical explanation. Since people usually surf by clicking on links, what do they do if there are no links on the page? Simple actually. They go to there bookmarks or type in a URL in the Browsers adress bar, and not knowing where the surfer will go Google asumes that each website on the internet has the same probability of being hit. So say thank you all you webmasters out there for all those selfish pages that try to keep all the "Green Juice" to themselves. Kinda makes you rethink nofollow.
This brings me to my next point. Since you are losing PageRank, link to pages outside your website to improve your visitores experience. This will actually improve your SERP rankings in Google. The rational is that a site that links out is a better recource than one that does not link out. Think of an acedemic paper that does not cite any other paper. It would seem a bit isolates, wouldn't it? This particular Rank is known as HubRank. It is not as valuable as PageRank becuase it can be easily manipulated ( You control the links as aposed to PageRank ) but it will do as a tie breaker between you and another site with a similar PageRank.
This leaves as with two question.
1. To what pages do I link?
2. Why not just link to more pages within my website?
Stay tuned to this blog and I will answer these 2 question in a future post.
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