What we know about (Google) PageRank.
Almost everybody is using it (or think they are), others believe they can manipulate it... but no body really understands very much about it. It is Google PageRank. It is probably one of the most important algorithms created for the web, and it continues to evolve even today Larry Page first invented it in 1995. Before we really start with the details let me just clear up a little misconception many website owners and web users seem to have. PageRank is not the Google Search Ranking (used when you search Google), yes its a part of it but its one of many thousands of other attributes to the Search Ranking system. So lets get into this... how does Google PageRank work? and What do we really know about it? This post is the culmination of my experience and my last 3 months worth of research into the effects of PageRank, how it works and various other theories around PageRank (so much i know i feel like writing a book). This post has been written to cut through the rubbish and jargon, though i do apologise for its complicated nature at times. Further more in the article I will only state what I know to be facts, I will save my theories on Google PageRank for another day.
What is PageRank?
"PageRank" (or PR) started of and continues to this day as only a rough estimation of the quality of any given website and the topical relevance of said website.
"PageRank" is one of many factors used by Google to determine a Search Ranking.
"PageRank evaluates two things: how many links there are to a web page from other pages, and the quality of the linking sites. With PageRank, five or six high-quality links from websites such as www.cnn.com and www.nytimes.com would be valued much more highly than twice as many links from less reputable or established sites." - Google Lib. Central
How Google PageRank Works
No body knows for sure exactly how PageRank works, however the below is what is generally accepted as being correct - Please remeber however that Google PR changes on a daily basis it appears.
The Equation: PR(A) = (1-d) + d(PR(t1)/C(t1) + … + PR(tn)/C(tn))
"In the equation 't1 - tn' are pages linking to page A, 'C' is the number of outbound links that a page has and 'd' is a damping factor, usually set to 0.85 ...
Lets make it easier to understand then ...
"a page’s PageRank = 0.15 + 0.85 * (a “share” of the PageRank of every page that links to it). “share” = the linking page’s PageRank divided by the number of outbound links on the page. A page “votes” an amount of PageRank onto each page that it links to. The amount of PageRank that it has to vote with is a little less than its own PageRank value (its own value * 0.85). This value is shared equally between all the pages that it links to." - WebWorkshop
PageRank is seen as a "voting" system, so a link from X to Z is a vote for Z from X ... but Google isn't just looking for volume. Google will analyse the site giving the vote, it will look at the relevance of the link, quality and importance of the site" - Read more about this from Google Technology
From the above we can deduce that not all links are the same, some will be more important than others... so if your site has a page rank of 7 and links to 1 site this "vote" will give more value than that if you have 1000 links from the same site... in effect the more links given the more your quality of vote is diluted.
Google PageRank uses what appears to be a logirithmic scale, meaning getting from one stage to the next is twice as hard as previously ... so getting from 0 to 1 is fairly easy ... but getting from 9 to 10 is ten times harder. - Read SEO Chats article on moving up the scale.
PageRank is not a value for the whole site, but rather an individual page within the site (this is often something over looked by website owners and SEO Companies). It is has been known that a page within a site can have a PR of 7 or 8 and other pages have 0 or 1 as PageRanks ... it is not a given that each page will gain ranking from the other pages of a site.
In general the public will see a PageRank update each month (only once), though in reality the PageRank algo is updated on a daily basis but the updates are only released to Google EXTERNAL servers at the end of an agreed period, this period is why Updates dont take place on the same date each month.
The "public" see page rank as an integer (aka 0 to 10, not 0.11) if you have been paying attention, you can probably understand this is a rounded figure (due to the algo). "“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." - Matt Cutts of Google
Links do NOT give away PageRank - this is a myth, nor do they leak it - PageRank of a web page is fixed by Google based on its algo (i say fixed this is to say nothing can suckle on it). A Link is simply a Vote!
"It often takes two full monthly updates for all of your incoming links to be discovered, counted, calculated and displayed as backlinks." - FAQs from SEO Chat
Dismissing the Myths of PageRank
There are a number of myths surrounding PageRank so its time to get them busted.
Updating or Adding content does NOT automatically mean you well get more PageRank automatically - dont forget there needs to be links for the algo to work!
Also add to this "Content is not taken into account when PageRank is calculated. Content is taken into account when you actually perform a search for specific search terms" - SitePoint Article
"High PageRank does NOT guarantee a high search ranking for any particular term. If it did, then PR10 sites like Adobe would always show up for any search you do. They don’t." - Search Engine Land on PageRank
Having a link from WikiPedia will not increase PageRank - they implement a No Follow model on all out going links.
Getting a link in DMOZ or ZoomInfo or YahooDirectory will not give you any kind of "Special" PR bonus! - The simple fact is that Google uses DMOZ for results only where the meta information is missing. However google isn't special in doing this, DMOZ the open-directory is used by many thousands of sites for this kind of information.
Having a sub directory doesnt mean that the sub directory will have less page rank than its root ... remember that pageRank is per page not site or directory.
.edu, .gov, .org sites do not have a higher PageRank "automatically" ... the fact is they tend to supply better content and have more links to them thats all... its PageRank working at its best.
Multiple links/votes from a page do not count as more than one vote.
Not all search engines treat the No Follow attribute the same - Google: doesnt use it for PR, or index the link - Yahoo doesnt use it as a vote but does index the link - ASK (formerly jeeves): does class it as a vote and does index the link...all pass the traffic.
Summary of Findings (this article)
So we've looked in some detail (though i have cut alot of crap out!) at Page Rank, how it works and some of the misconceptions. So here are the Top 10 things you should be takings from this article.
<h4>PageRank does NOT mean search rank - it is a part of it though.</h4> <h4>PageRank is about links, a link is a vote, the more links on a page the less they are worth ... but you do not leak pagerank via links.</h4> <h4>PageRank is for a page not a site, and is based on incoming links (or votes).</h4> <h4>Bad incoming links don't impact on PageRank, but link farming does.</h4> <h4>PageRank is expodential, meaning its harder to get between points... also PageRank should be seen as a float of % not an integer.</h4> <h4>High PageRank does not mean a High Search Rank.</h4> <h4>The level of the domain doesn't automatically mean high PageRank.</h4> <h4>Wikipedia links don't count towards PageRank.</h4> <h4>No Follow links don't count towards PageRank.</h4> <h4>Links to and from high PageRanked sites can have an impact on PageRank.</h4>
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