Downgrade Pagerank
When a page’s PageRank decreases it is easy and common to assume that Google has issued some sort of penalty. In many cases this is true, but in many other cases, it isn’t. Here are some of the reasons why it happens.
Increase in Google’s index
This is natural, and yet it is the least known reason for PageRank reductions. The page’s PageRank doesn’t go down; what goes down is the Toolbar’s representation of it.
Google divides the number of pages in its index into 10 sections, and each section is represented by a number, between 1 and 10, in the Toolbar. For simplicity, let’s assume that Google has 100 pages in it’s index, and let’s assume that Google divides the total number of pages (100) into 10 equal parts. You may imagine that the pages are sorted in numerical order according to their PageRanks. For the first 10 pages, the Toolbar will show “1″, for next 10, it will show “2″, and so on. This is where the Toolbar figure comes from. It isn’t actual PageRank definitely; but it’s just a representation of which PageRank division page is in. Now let’s double the size of Googles index by adding 100 new pages to it. The new pages will have their PageRanks calculated and they will take their place in the numerical list. The total number of pages is divided by the 10 Toolbar section, and we find that there are now 20 pages per section. The point here is that the old pages that were in the old 11 to 20 (PR2) section, now find themselves in the 1 to 20 (PR1) section. Their actual PageRanks haven’t been reduced but they have moved down a division because of the addition of all those new pages. That is often the reason why a page’s PageRank drops a Toolbar point. We shouldn’t really refer to the Toolbar figure as PageRank because it isn’t. It’s a division, and that’s all. In reality, Google divides the number of pages on a log scale (or similar), and not into equal parts. Also, the index grows in much smaller increases, so pages dropping down a division is common but not as widespread as a doubling of the index would be.
Penalties
When a page drops several Toolbar points, often to PR0, it is the result of a penalty, though not necessarily a penalty that has been applied to the page itself or even to the website. Penalties are applied when Google finds things about a website or page that they don’t like. E.g. involvement in link farms, doorway pages, multiple domain techniques, hidden text, cloaking, etc.
Link penalties: Google’s view is that webmasters cannot control which websites and pages link to their sites, but they can control where their own sites links to. Linking to a penalized page or site, or a page or site that is later penalized, can attract a penalty for the linking site.
Other reasons
It is possible to find a reduction in the Toolbar figure following the update after making internal link changes. I.e. by changing linkages, it is possible to divert the PageRank within the site to different pages.
Tags: pagerank, pr2, pr1, google, simplicity, log scale
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