What is the PageRank Number?

The PR number is calculated as a probability a random surfer ends up at a certain webpage by following links.

First of all it means the PR number for page A depends only on incoming links to page A.

Second the PR number (page A) is affected by the PR number of the page where the outgoing link is (page B), if the content is relevant or not, and some other page factors.

Say, for instance, there are 10 outgoing links on a webpage. Then the probability the surfer chooses a certain one is 1/10, i.e. 0.1. If no other factors would be considered, the value of the link would be PR number divided by 10, i.e. PR value times 0.1.

The final calculation isn't, however, that straight forward. The PR number to be distributed is modified by several webpage specific factors on the webpage where the outgoing link is:
- page specific factors (content)
- link anchor text
- other factors

The link is more "valuable" for you when

• the content is relevant to the target page,
  
• the content on the link page is up-to-date,
  
• anchor (link) text is "normal", i.e. not same for every incoming link,
  
• different links are coming from different IP numbers,
  
• the link is one way only (not a reciprocal one),
  
• embedded in the text, instead of coming from a "resource page".

Once the probability has been weighted with all other factors it`s really not a probability anymore. Neither is it intended to be, the PR number is intended to indicate a value for each incoming link to a certain webpage.

Because the PR value of each incoming link depends partly on the PR number of the page it comes from, it`s said the incoming link gives a portion of a webpage`s PR number (value) to the target page. In a sense it is so, but it`s giving without taking anything away from the page where the outgoing link is.

As when you give somebody your trust you don`t diminish yourself in any way. Except if it happens to be a bad person or a person who later turns out to be bad.

The PR number of the target page is then calculated as the total value of all incoming links. As this sum is easily above 1.0 it cannot be a probability anymore. As per definition the PR number of a webpage derives only from incoming links. Therefore not a single outgoing link on page B affects the PR number of webpage B.
 
The PR number for a webpage is a value estimate for that webpage. It has no direct connection with a webpage`s ranking in any SERP, because the number is unchanged, regardless of any keywords or key phrases. Google's own PR is 10/10, but that doesn't mean every surfer always ends up at Google.

If you have a big website with plenty pages you need also a lot of incoming links, preferably at least two incoming links to every one of your pages. You can "distribute" some of the PageRank on the "top pages" to those pages without any incoming links but the effect wouldn't be as strong.

A page with PR-number 01/10 can very well appear as #1, while a page with number 03/10 can appear as #5 on the same results page. See Google's own explanation of the PR-number and Search Engine Land's overview (April 2007) and How to Calculate PR.

In January 2008 Yahoo made a patent application containing a method for including internet user behaviour in the pagerank calculation. They call it User-sensitive pagerank. It could be taken as either a further development or just a small twist to make it possible for Yahoo to patent their own version.

What about PageRank = 0 ?

Because the PR number derives from incoming links only, a zero means that

• There are no or only very few incoming links, or
  
• There are almost only hidden incoming links.

If a page has no incoming links, then Google cannot find it and it cannot be registered - so the PR number is of course zero.

So what about hidden links? You can add to the http reference code rel="nofollow", in which case Google and some other search engines will ignore the link, i.e. it`s not registered by them. Or you can write the link reference in JavaScript, which search engine robots cannot read, and of course they will disregard the link with the same result.

Why would anybody do that? It can be reasonable to hide your link, for instance to a printer friendly or a pdf version of your webpage to avoid duplicate text. But some webmasters (very few) hide their outgoing links, especially on their resource pages. In that case those resource links stay hidden.

This is a very foul trick. May be they give you a link and ask for a return link, and what happens? What you get is a hidden link no search engine knows anything about. The other webmaster gets some PR from you while you get nothing in return. Hopefully this is done in the mistaken belief that they preserve their own PR number!

Google`s toolbar

The PR number Google uses to evaluate webpages is one thing and the PR number in Google`s toolbar is something else. The real PR value number only Google knows.

To see the PageRank Number (PR) you need the Google toolbar. When you put your mouse arrow on the Page Rank bar a yellow rectangle pops up with a number between 01/10-10/10. If you don't have or don't want the toolbar, you can use Webmaster eyes, which shows you the PR number for any URL. The PR number in the toolbar (01/10 to 10/10) should be taken as a label only, indicating where on the scale a webpage is situated, is it at the bottom, in the middle, or at the top?

The scale cannot be stationary but must be flexible (stretching) because total number of webpages is continuously increasing. As the number of webpages in each category increases, also the threshold values increase. In other words, if a page is just above the threshold value for 04/10 it will drop to 03/10 if no more incoming links when number of webpages in category 03/10 increases.

A white toolbar means the webpage is registered but PR = 0, while a gray toolbar shows that the webpage isn't registered with Google at all.

Many "students" of Google`s PR number agree the scale is logarithmic. With such a scale you get the effect that you need a much higher increase of the PR value number, or many times more incoming links to move from PR 04 to PR 05 compared with moving from PR 03 to PR 04.

Google PR and Webpage Rankings

As said above, the PR number depends only on number and quality of incoming links. However, you must remember that your webpage is just one in a "never ending" chain of links and whatever anybody does with his/her webpage in the chain before your page also affects your PR number - the real one that only Google's engineers know.

What you see in the toolbar is as well an indication only, and as it is only periodically updated it can easily be 4-5 months old. The real one sure affects your rankings on Google's search results pages - but it's only one factor of many others included in the ranking algorithm.

In 2007 Google up-dated the published PR-number first week of April and the next up-date was only during the last week of October, i.e. 6 months later.

About middle of January 2008 there were some reports on a new PR up-date. This seems to be correct so far as some "nonsense" ( not so good ) incoming links were deleted from the records. Of course, if a website was before just a fraction over the threshold, say 04, then very little would be needed for the published number to drop to 03/10.

I compared listed links on January 01 and February 01 ( Webmaster's consol ) and Google had culled close to 10% of total number of incoming links. The discounted ones were all nonsense links of no value and at the same time a number of good relevant incoming links were added, so the total number lost was about 6%. In fact this worked out as a consolidation of my incoming links base giving a stronger relevant base (my employment portal website). I view this as an algorithm tight-up, may be connected to the fight against link buying.

The actual ranking on the search results pages each day or week or month is the only measure you can use if you want to check the effects of your optimizing efforts. But keep in mind it's not only what you do that has an effect, also other webmasters' work affects your result. The greatest effects come of course from your own and your linking partners work with the webpages.