Internal PageRank (or PR) leak
The previous pages tried to show the effect of linking between sites. A link does not only affect the linking and the linked pages - but has an effect on all surrounding pages.
Still, this doesn't alter our basic understanding of links: We know inbound links are good, without having to know the exact value in real PageRank.
In the same way we know that outbound links cost us some PageRank - but they may be worth it. A link to a good resource may make our site more valuable to our visitors, and maybe the other site will even link back. But there's another trap we should always avoid: the internal PageRank leak.
Hagstrøm's second law: There is not an equal and opposite increase in PageRank for every PageRank leak.
Consider a small site like the one to the left.
|How to specify the pyramid structure|
The result is that the site has a total PageRank of 8 - as shown on this spreadsheet.
|Introducing an internal PageRank leak|
As the spreadsheet shows, the site has lost more than 25% of its total PageRank. After 12 iterations the total PageRank is no longer 8 but 5.8955.
These internal PageRank leaks have all the costs of an external link - and none of the benefits. They may be caused by several things, like:
- Pages not linking back to the rest of the site (like in this example)
- Pages that are protected by the robots.txt file
- Pages with the Meta tag "robots nofollow"
- Pages that doesn't exist, or have been renamed
A slight variant in the real Google-world is where a link does not follow the convention used on the rest of the site. Technically the following are four different pages: