PageRank is an algorithm which analyses the link structure of a hyper-linked set of web pages and then assigns a numerical weighting to each page as a way of measuring their relative importance within that set. The PageRank of a particular web page is an indication of its value within the Google index. The scale is a range from 0 to 10.
A page with high PageRank will have a direct positive effect on its spot within search results, but it is not the only factor considered by the Google algorithm when ranking a page – it is only one of approximately 200 factors but it is, none the less, one of the most vital.
This is how Google describes PageRank:
PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual pages value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves “vital” weigh more heavily and help to make other pages “vital”.
As a website starts to increase in popularity via the feature and quantity of back links, the PageRank of a particular page also increases. This increase in number but is based, we believe, on a logarithmic scale. As an example if using a base 10 scale, to get a PageRank of 1 the page requires 10 back links pointing to it, then to gain a further point on the scale, the page will require an extra 100 backl inks, to gain a further point an extra 1000 back links will be required and so on.
Retaining all of that valuable PageRank can be tough and a lot of it has to do with how the internal between structure of your website is set up. It is very simple to leak ‘link juice’ from vital pages into less vital pages that are less likely to appear in search results. There are methods available to search marketers that allow us to reduce this leakage commonly referred to as PageRank sculpting.
A further way of leaking ‘link juice’ is to have large amounts of outdoor between to other websites without getting a similar amount of links back into your website. As part of the link building process Search Marketers are constantly aware of checking the likely value of a link from a particular website previous to they leak any ‘link juice’ out to that site via a reciprocal link.
As you’ll know by now, even if PageRank is a critical component in Google’s ranking algorithm, due to its logarithmic nature it is very hard to obtain a high PageRank even after years of link building. By its very nature, the web changes and the page that a link comes from may not carry as much weight as it did when the link was first obtained, regardless of the PageRank measure for that page. It could simply be that other pages that were ‘voting’ for that particular page may not carry as much weight as they once did which has a flow on effect to the value of the link going to your site.
Google advise that the PageRank assessment of a webpage is calculated on a fixed basis but that the PageRank scale shown on the Google Toolbar is only updated 2-3 times per year so the very best option for all websites to gain rankings is to take up again to build credible back links and not to be discouraged when the PageRank scale doesn’t slide upwards overnight.