Ok as I said in the previous two posts, I am currently reading Aaron Wall's SEO Book, and part of it discusses Page Rank and how that is computed by Google to show what is called "Authority" to compute relevance for a given search term. In case you are new to SEO, it is the optimization of your site and creating relevant back links that enables you to place high within search engine results for given keywords.

This is really important because in order to generate a lot of relevant traffic - read traffic that does not bounce but converts (signing up members, selling produts, etc...) you need to focus on linking with certain keywords. What does this have to do with Page Rank? Well Google assigns a page rank to every single page on every single website it indexes. And many people have downloaded the Google Tool Bar which allows you to see a site's page rank. Here is where the myth begins.

The Google Tool Bar, I have discovered, is really misleading for several reasons:

1) Page rank - which is listed as 0-10, is actually a floating point number! A floating point number is a number with a decimal point that represents fractions. So actually there are really fine gradations between all page ranks.

2) Google does not update their tool bar very often! Actually it happens about once every three months or so. However, the real page rank - the one stored in the Google search algorythm is CONSTANTLY CHANGING, and as I said before is actually a number with a decimal point. So a PR 4 website may be listed in the Google index as PR 4.01334. Which means that not all PR 4 pages are equal!

3) I have a PR 0 site that is now getting a lot more traffic from Google than a PR 3 website that I have, which means that Google has not updated their tool bar, and in fact my PR 0 site may have a higher internal page rank than my PR3 one.

I had come to these conclusions on my own recently after looking at my traffic logs, but I also confirmed my suspicions when I did a search to find comments from Matt Cutts - a Google employee who had the following comments to make on Page Rank.

Page Rank as a floating point number - "It’s more accurate to think of it as a floating-point number. Certainly our internal PageRank computations have many more degrees of resolution than the 0-10 values shown in the toolbar."

How Google's Data Centers Transfer Page Rank which may cause a delay - "The latter. I think most data centers are running the newer infrastructure for things like info:, related:, link: and PageRank, and I believe every data center that has that newer infrastructure has the recent snapshot of PageRank now. I wouldn’t be surprised if it took at least 1-2 months for the other data center IPs to get the newer infrastructure in some way. (Yes, this is smaller, different infrastructure than the stuff that made site: queries have more accurate results estimates.)"

Page Rank is computed continuously - "I believe that I’ve said before that PageRank is computed continuously; there are machines that take inputs to the PageRank algorithm at Google and compute the resulting PageRanks. So at any given time, a url in Google’s system has up-to-date PageRank as a result of running the computation with the inputs to the algorithm. From time-to-time, that internal PageRank value is exported so that it’s visible to Google Toolbar users (see the question below for more details on the timing)."

You can read the full article here http://www.mattcutts.com/blog/more-info-on-pagerank/

You can buy Aaron Wall's SEO Book Here