Google PageRank Primer

GoogleAs people become more familiar with the process of optimizing their web sites for rankings in Google, the term PageRank appears in many of their discussions. In fact, lately, we’re reading and hearing a lot about Google PageRank. The purpose of this article is not to be a definitive answer on the topic of Google PageRank (or PR). Instead, it provides some basic answers, to some frequently asked questions regarding PR.

What Exactly is PageRank Anyway?

PageRank (spelled as one word) is a trademarked technology, belonging to the search engine Google. It was designed as a numerical system of ranking the relative importance of web pages, created at Stanford University in California, by Google founders Larry Page and Sergey Brin. The concept they used was, in Google’s own words, to calculate the “uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page’s value.”

If Google’s definition is taken literally, the entire system rests on the incoming and outgoing links, from the billions of web pages that form the internet. On the surface, the system seems simple enough. If web page A links to web page B, Google considers web page A as actually voting for the importance of web page B.

Of course, like anything else in life, the reality is far more complicated than what it first seems.

Be sure to always keep in mind that PageRank is not the same thing as your site’s ranking on the search engine results pages (SERPs). They are entirely separate items. PR is the relative importance of a page on the web, expressed as a number. The SERPs are where your site appears on a search for your keywords.

PageRank Numbers

Note carefully that PageRank is for each individual web page, not the entire web site as a whole. Every page in the Google data base has its own PageRank. In other words, sites don’t have “rank.” Rather, every separate page on your web site has its own PageRank.

Incoming links for web pages are, in the opinion of Google, votes in favor of that page. On the other hand, Google considers some votes to be more important than others. The simple number of incoming links to a page is calculated by Google, but the relative importance of the “voting page” is given even more weight in the mathematical formula.

The pages that are considered to be more important votes, in turn increase the importance of the page they link. More important pages pass along more voting power. This is measured numerically as PageRank.

The PageRank numbers range from 0 to 10. These numbers are usually expressed as PR0 (for PageRank 0) to PR10 (for PageRank 10).

What do these numbers mean?

First of all, you need to find out what your PageRank is, for every page on your web site. To do that, you can download the Google Toolbar. It can be found at http://toolbar.google.com/ and can be downloaded and installed in your browser in just a few minutes.

Note: Unfortunately, the Google Toolbar is not available from Google for Mac users.

When the Google Toolbar is loaded, you will see a green line shaded from left to right, located under the word PageRank. Wave your mouse over the gauge, and words will appear stating the Google PageRank “importance” of the page being examined. The Toolbar will give you the PageRank for every web page you visit.

A PR0 page will show a blank white gauge, while a PR10 page will have the entire PageRank indicator filled in, with green from side to side.

When a page has a PR0, it is either below the threshold for a PR1 in Pagerank, is a brand new page, or is under a penalty from Google. Pages that show a gray colored bar, in place of green or white, are either not included in the Google index, or are under a substantial penalty for violations of Google’s rules.

The PageRank number shown on the Google Toolbar, is thought by many people, to be merely an estimate of a page’s true PageRank. While there is no real proof, one way or the other about the accuracy of the PageRank as presented, we can only assume is a good estimate. Only Google knows the actual PageRank, and they aren’t talking.

PageRank is not a series of equal steps; it is logarithmic in its calculation. In the same way that the earthquake Richter scale is exponential in calculation, so too is the mathematics behind Google PageRank. It takes one step to from a PR0 to a PR1. It takes a few more steps to PR2 and PR3. Now, it takes even more steps to PR4, many more steps again to PR5, and so on. Each level is progressively harder to reach.

Let’s consider an example.

For illustration purposes, think of a PR5 page. It is indicated by the PageRank meter being half green and half white. What does that mean?

Google PageRank is not a series of stepped numbers, as presented on the Toolbar. It is more of a continuum where our PR5 example may be barely over the boundary from being a PR4, or almost but not quite, a PR6 page. There is a lot of territory in between.

For our example page to reach a PR6, it will take many more incoming links, and perhaps higher PR pages as well, to reach that new higher level. It will be much more difficult to increase from a PR5 to a PR6, than the move was from PR4 to PR5.

PageRank is a form of a voting system. A link to a page is a vote for that page. Higher PageRank pages are viewed by Google as more important. Their votes are given more value by Google. In some cases, much more value.

Adding incoming links to your web pages will add PageRank. Every inbound link adds some PageRank, regardless of its own level. PageRank flows from one page to another, adding to its store of importance.

Not all incoming links provide the same inflow of value. It may take many PR2 incoming links to increase your targeted page to PR5. On the other hand, it might only take one PR6 page to give you the same result.

Google has published their original PR calculation formula:

PR(A) = (1-d) + d(PR(t1)/C(t1) + … + PR(tn)/C(tn))

While we are not certain if this formula is still the one used by Google, it is probably at least very similar.

In the formula, PR(A) is the PageRank of the page = (1- d) where d is a “damping factor considered to be about 0.85 + d(PR(t1) where t1 is the PR of the incoming link page + …+ PR (tn) is the Page Rank of all of the linking pages. Each page is divided by C which is the number of outgoing links from each page.

Note that the PR flow from a page is divided equally between all of the links on the page. If a page has one outgoing link, that receiving page gets the entire flow. If there are ten links on the page, the PR flow is divided ten ways, lessened by the 0.85 damping factor.

Simply put the formula is this:

PR(A) = .15 + .85 * the PR share of every incoming link page.

Based on the formula, the more incoming links from higher PR pages the better. On the other hand, fewer outgoing links from the sending page, the better too. You get less PR if it’s divided among more outgoing links. Everyone gets their share of the PR pie. Your piece simply becomes smaller if there are more mouths to feed!

You can theoretically gain more total PR from a PR4 page, where you are the only recipient, than from a PR8 page divided 100 ways.
The bottom line is to add, within the context of an overall linking program, as many incoming links as you can. They all add PR to varying degrees.

Google only lists your incoming links that have a PR4 or higher. Because of that display restriction, many people believe Google doesn’t count all of your links in your PageRank calculation. While they are not shown, Google counts them all. The lower PR pages may not bring a lot of incoming PR with them, but they all add up, although in much smaller increments. Don’t ignore lower PR pages for link exchanges, as today’s PR2 may be a PR7 in the very near future.

You need to keep adding more incoming links to maintain your site’s PR. As you link out from your site, it’s thought that PR “leaks” to other sites. While not everyone agrees on whether PR leakage actually occurs, it’s a good idea to keep your PR increasing. Keep in mind that Google considers internal links, within your site, as backlinks. They add to your overall PageRank. They can’t, however, do the job by themselves. Outside sources of PR are still required to fuel their PR.

While Google isn’t saying, it’s doubtful that you can double or triple PR flow from one page to another, by adding more than one link to a page. It seems as if Google only counts a link to a page once.

In much the same way, and again Google is tight lipped on the matter, a page probably won’t have a link counted by linking to itself. That is not the same as other pages within the same site linking to the page. They count. Remember, its page PR, not site PR.

Some Tips on Link Exchanges

When requesting exchanges, always request the page upon which your link will appear. Don’t let your link trading partner place you on a PR0 “links page” with hundreds of other outgoing links. Make certain they don’t use a java link that prevents the passing along of PR. Another thing to avoid is the discovery that your links have been hidden or cloaked. Make certain all link exchanges are fair and equitable ones, that pass along the appropriate Pagerank.

Don’t fall into the habit of only considering link exchanges, or soliciting incoming links from high PR sites, just for the sake of PR. While they are good to have, be sure to consider the value of your linking program from your visitor’s point of view. It’s more important for links to be helpful to your visitor traffic. Your goal is sales. The PageRank is only part of the means of getting there.

As your PageRank rises, it can help you move higher in the search results, for your targeted keywords. While PR is only one of about 100 or so factors considered, in the Google algorithm (the mathematical formula used to determine your site’s location in the search results), it is still an important consideration.

As you add more and more incoming links to your many web pages, you should see a rise in your PageRank.

After all, it’s simply a mathematical formula at work.

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