Summary: PageRank measures the amount of votes for your page/site, in order to determine which sites are best. A page that links to you is voting for your website. Pages/sites with the most votes from other good sites appear higher in the search engine listings.
It’s useful to have a general understanding of page rank, so you can see what exactly it is you’re aiming for with your link building campaign. Here, we’ll try and explain it as simply as possible – however, page rank isn’t a particularly simple concept!
Background
PageRank is an algorithm that analyses links, named after Larry Page and used by Google. It works by giving each page on the web a rating, which determines how important that page is in relation to other pages.
The word ‘PageRank’ is actually trademarked to Google, and the process itself has been patented, although the patent is assigned to Stanford University, not Google – with Google having exclusive license rights to the patent.
Simplified version of algorithm
To explain how the page rank algorithm works, imagine the web contains just four web pages – (a) (b) (c) and (d). As a starting point, we could assign an equal page rank between those four pages. This would give each document a page rank of 0.25.
Now let’s assume that page (a) is the most important page. As a result, pages (b), (c) and (d) all have a link to page (a). Consequently, they each give 0.25 page rank to (a).
The page rank of (a) is therefore the page rank of (b), (c) and (d) added together.
Let’s complicate things a little and assume that page (a) is the most important but page (c) is also quite important. So page (b) also links to page (c). Further, page (d) now links to all three pages.
Whilst each page had 0.25 ‘worth’ of page rank to pass over, the value of this is divided by the number of outbound links on a page.
So with page (b) now linking to both page (a) and page (c), those votes from page (b) are only worth 0.125 each.
With page (d) linking to all three pages, the value of (d)’s ‘vote’ is now only 0.083.
Damping factor
You might think, having got your head around this formula, that you can actually calculate the value of obtaining a certain number of links. Unfortunately it’s not so simple – there is a ‘damping factor’ that has a part to play. PageRank is a probability distribution that is used to show the likelihood that a person randomly clicking on links will arrive at any particular page. Without going into too much detail, the damping factor adjusts the page rank calculation downwards, because it is assumed that even an imaginary surfer who is randomly clicking on links will eventually stop clicking. It’s not known exactly what the damping factor is, in value.
Do I need to know all this?
Not really. What you do need to know is that you need good quality links from relevant, trusted and authoritative sites in order to get your site ranked better. We have included many articles on link building for these kind of links in the knowledge base.
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