PageRank (after its inventor, Lawrence Page and Eng. Rank - Rank) is the Google system used for the evaluation of the listed sites. The basic principle is: The more links to a page, the more important it is. The more important turn the referring pages are, the greater the effect.

The Google PageRank displayed is between 0 and 10. Normal websites have a rank of 1-5. Important pages or optimized to achieve values of 5-7. Pages with a PageRank of 8 and higher are very rare, for example, the White House, the corporate side of Microsoft or check.

The higher the PageRank of a page, the better will be listed in Google.

The system worked well so long to link Seo’s strategists and began the PageRank system to understand and manipulate. Many text links from PageRank strong links topics alien rented or exchanged. The result of this manipulation is that many search terms for the first hit of the result pages are no longer relevant and the web pages with the most corrupt links to the front seats.

Since November 2005 Google seems a theme-based PageRank. This should improve the situation and again relevant search results.

The idea behind the theme-based PageRank is, is the following:
The search engine takes account for each link to a Web page shows the content of the page and the left calculated from the topics based Backlinks this page the link weight, so the themes-based PageRank of links and the link then qualified for the search phrase. Links that are not part of the search phrase fit into account in the calculation of the themes-based PageRank (Topic sensitive PageRank TSPR) not to.

Google hopes, thus creating the conditions to create a mere manipulation by setting link with a link text impossible. Links from topics foreign pages for the search phrase thus worthless.