The Search engine's purpose is to provide useful, high quality and relevant information for any search term. There is a real war between the search engines' methods and algorithms and search engine optimizers. The result must be the user's satisfaction: high quality web sites in high positions on the search engines lists. Page Rank is an indicator that Google is using to measure web sites popularity. The algorithm to establish it is a secret, but it is easy to find that the most important factors can be the number of links leading to the website page and the Page Rank of the link’s source.

It looks like the most popular search engines are counting the links (incoming or outgoing) and considering their number like a vote for quality. In reality, not each link is equal in quality to the others. Search engines are considering the link's quality as very important; maybe this is the determinant factor to establish a page rank. Google is the first search engine taking this factor into account. Search engine optimizers are trying to do their best to find the top quality links for their web sites. But there are many types of links. They must find the ones giving high ranks all the time. Everybody agrees that links from high quality web sites are a major gain for a page rank. There is also the possibility to build links from related sites. In this situation, the sites must have many topics in common.