Note from Ann: I’d like this post not to turn into another “PR algorithm” one. Instead, I’d love us to discuss how many of us still use this information and how we do that. So please, share your opinion in the comments!
One area of SEO that is limited to one search engine but gets plenty of attention is Google PageRank. This is a core element of Google’s search algorithm, created before Google was even a publicly known company. Most SEOs and web designers are aware of it, but knowing just how it operates is another thing entirely.
The full functionality of PageRank has changed some over the years, but how it is distributed is still very close to the original algorithm Larry Page developed at Stanford. That full algorithm is as follows:
PR = 0.15 + 0.85 ( PR(Backlink 1)/TotalLinks(Backlink 1) + PR(Backlink 2)/TotalLinks(Backlink 2) + … + PR(Backlink X)/TotalLinks(Backlink X) )
In other words, the PageRank for any given page is calculated by adding 0.15 to 0.85 times the PageRank for each page linking to it which is divided by the number of links on that page linking to it. In English, this means you have a starting value of 0.15 for a page with no links pointing to it, then for each link, the amount added is affected by the PageRank of the backlink and affected by the number of links out from that backlink.
Most SEOs know that you want high PR pages to get for backlinks. Just keep in mind the fact that the link juice you get from any backlink is spread across every link from that page. So if you get a backlink from a PR6 site but that page has hundreds of links, it may not be as good as getting a link from a PR4 site with only three links leaving that page.
This also affects on-site SEO. So if you want to share the PageRank of your main index page with the rest of the pages on your site, be careful with how many links you set up on that index page. Even though you might have targeted anchor text in the hundred links you have in your footer, if you have a hundred links, you won’t be sharing much PageRank with each of those pages.
Knowing these details about PageRank can help you locate higher quality backlinks for your SEO, and can make the difference between a good backlink and a great one.
You can check back on Eric’s blog for more information on PageRank explained.