Google Page Rank Explained
PageRank is one of the many methods used by Google to help determine the importance of a web page. Developed by Larry Page and Sergey Brin, the founders of Google, while at Stanford University, PageRank became one of the main tools used by the Google search engine. Before I go any further I must give you a word of warning here - Google is very protective of exactly what factors are used in its search engine algorithms, and exactly how those factors are determined. What follows here is believed by most industry experts to be correct in essence, though some of the details may not be fully accurate.
In simple terms, Google describes PageRank as a method for determining the value of a web page by the value of web pages to which it is linked. In other words, a link from web page A to web page B is considered as a vote by page A for page B. However, Google does not just look at the number of links that a web page receives; it also looks at the PageRank of those pages. A link from a web page with a high PageRank is considered to have more value than a link from a web page with a low PageRank.
The value of a web page can be between 0, the lowest value, and 10. However, this is not a simple linear progression, but rather some form of logarithmic progression – it takes more links, or links of a higher quality, to move from PageRank 6 to 7, than it does to move from 1 to 2. Google doesn't state exactly how their scale works, but let’s assume that is actually logarithmic. If so, then for example if it takes 10 links to move from PageRank 0 to 1, it would take 100 links to move from 1 to 2, and 1000 links to move from 2 to 3. This assumes of course that all links are of equal value.
Now, so far we have been talking solely about PageRank in terms of individual web pages. However, a web site also has a PageRank. This can be determined by adding up the PageRank of the individual web pages. The total PageRank for the whole web site can never be higher than the total number of pages on that web site. In other words, a web site that consists of just five pages will have a maximum potential PageRank of 5. Note the word potential there – that site may never reach that particular PageRank – but without adding more pages there is no way that the site will ever reach a higher PageRank than 5. Note that not all web pages within a site will have an identical PageRank – the web pages with more incoming links will have a higher PageRank than those with fewer links.
I mentioned above the importance of the value of the links to a web page. I don’t want to get into the math too much here – there are many examples of this to be found on the Internet – but I will try to explain this in simple terms. The value of a link is determined by the PageRank of the page from which the link comes. However, the value of that link is divided up between all of the links from that page. So, for example, a link from a web page with a PageRank of 6 and only three outgoing links is worth more than a link from a similarly-ranked page with twenty outgoing links. This holds true for web pages with similar rankings, but, due to the nature of the PageRank scale, becomes less of a factor as the difference between PageRanks increases. The amount by which that factor decreases is open to argument since Google won’t reveal all of the factors that go into determining PageRank, but it is safe to assume that if the PageRank is significantly higher then it doesn’t matter how many links are on that web page.
So, in conclusion, what does all of this mean? As I mentioned at the start, PageRank is just one of the many factors used by Google when deciding how a web page should be ranked within its search results. The exact importance of PageRank within those factors is something that Google alone knows – everything else is pure speculation. There is some talk that PageRank has been devalued of late, with less weighting given to it than previously was the case. However, PageRank is still something that a web site owner or administrator should take into consideration when designing a web site. Links do still matter in search engine optimization and the higher-quality links matter more.
Updated : Mon - 01 July 2019