How Google decides PageRank

In the SEO community there is a lot of focus on PageRank as an indicator of a domain's worth. Although it is probably one of the most important factors in a domain's value in the eyes of Google, there are a few things that should be understood. Google PageRank has eleven scores, between 1 and 10. Web pages that don't have any PageRank are often symbolized as having N/A PageRank. The higher the PageRank, the more likely Google is to trust it. This is true for both external and internal hyperlinks. Google assigns each page on the Internet a value and when one web page links to another it passes some weight onto the page it is linking to.

To begin with, for anyone who doesn't know what PageRank is - it is a value used by Google to decide how important a domain is based on analysis of hyperlinks. So, if a web page has 4 PageRank 4 and 3 PageRank 3 links pointing at it, it will probably be give a PageRank of 4. PageRank is generally not assigned to a page higher than the pages that link to it. The most important factor in the assignment of PageRank to a web page is the PageRank of the pages linking to it. The higher the PageRank of web pages linking to a given page, the higher its PageRank is likely to be. It should be noted; web pages that have a lot of low PageRank and PageRank N/A hyperlinks pointing to them can have their PageRank reduced as a result.

A site can have a high PageRank with relatively few links pointing to it if those links are of a high PageRank. The sheer quantity of links does not help to increase PageRank. Some suggest that the text content of a page affects PageRank assignment, but this doesn't seem to be the case. There is no substantiated evidence that text affects PageRank other than pages that have been spammed often have their PageRank reduced. When it comes to sub-pages, the time Google has known about them is a factor in PageRank distribution. When new sites first get given PageRank their sub-pages often remain without any PageRank. In general, sub-pages are somewhat slow to get give PageRank. Google is generally less trusting of sub-pages unless they belong to a trusted domain. In particular sites with a lot of sub-pages and even more so sites that link to a lot of internal pages (like directories) can really struggle to pass their PageRank to internal pages.

The architecture of the site has a major role to play in the assignment of PageRank. Google uses what is known as block level analysis to pick apart web pages. They use their vast knowledge of the structure of the web to decide what links on a page are probably the trustworthiest and the pages these links point to are more likely to be assigned PageRank. Google can and do modify websites' PageRank. This is generally as a penalty for sites that have used unhonest methods. This can often cause all the site's sub-pages to loose their PageRank. It has also been claimed that in the past Google has made mistakes in PageRank distribution. Lastly, the PageRank of a web page may change even when there has been no change in the hyperlinks pointing to that page. This is either due to changes in the structure of links between all websites or modifications made by Google.

Sky Alfaro is an SEO consultant with the SEM Labs SEO Agency where she helps small to medium sized companies with search engine marketing training.