PageRank algorithm
Introduction
PageRank is one of a number of algorithms (Maths formulas) that measures how relevant and useful a particular website page is. It is used by Google Search to organise the results of a search into a ranked order of importance and relevance.
How does PageRank work?
PageRank is based around the idea that the more links there are to a web page, the more important it is. If peers link to one of your web pages then it must be a good sign that the web page is probably useful, relevant, up-to-date, informative and worth being higher up a list of results than a web page that has no links to it.
PageRank works by assigning a numerical weighting to each web page in a website, looking at, for example, the number and quality of links to each web page (amongst other factors). Each link is considered a 'vote' for the web page. It also looks at the number of links on the web page that is linking to a web page it is ranking! This makes a lot of sense; if someone links to a page on your website from one of their web pages, and they have in turn many links from other people to that web page, then they are probably more 'important' or knowledgeable than someone who links to you but has no one linking to them. The web page that linked to you and has also lots of links on their webpage will have a more important vote when it comes to working out the ranking of your web page compared to someone who no one links to. This is true for someone who has a reasonable number of links to other web pages. However, if they start putting too many links on a web page, this is picked up by PageRank and the importance of their vote is decreased. Other factors that might affect a ranking include how frequently a web page is updated, the age of links to and from web pages, how 'good' the domain name is and so on. PageRank is constantly being adapted and improved.
You as a website owner can improve your PageRank by swapping links with other genuine and relevant website owners but the easiest way by far is to ensure that your website is so good that people want to keep visiting it and linking to it naturally!
Problems with PageRank
Whenever people work out how an algorithm works, how algorithms are used to rank search engine returns, they can be manipulated. Google Bombs are a case in point. This is where a group of people agree to artificially increase the ranking of a web page by artificially linking words and phrases to it. Google adjusted its algorithms to counter Google bombs but the problem still exists.
Link farming is another method used. This is where links are created in web pages to other web pages automatically using software, but without any concern as to how relevant the links are. You may well have come across web pages that are essentially just full of links to other web pages. This may be a link farm. Again, Google is proactive in its fight against link farming but the battle never ends!