What is PageRank?

Google describes PageRank:

"PageRank reflects our view of the importance of web pages by considering more than 500 million variables and 2 billion terms. Pages that we believe are important pages receive a higher PageRank and are more likely to appear at the top of the search results.
PageRank also considers the importance of each page that casts a vote, as votes from some pages are considered to have greater value, thus giving the linked page greater value. We have always taken a pragmatic approach to help improve search quality and create useful products, and our technology uses the collective intelligence of the web to determine a page's importance."

A PageRank results from a mathematical algorithm based on the graph, the webgraph, created by all World Wide Web pages as nodes andhyperlinks as edges, taking into consideration authority hubs like Wikipedia (however, Wikipedia is actually a sink rather than a hub because it uses nofollow on external links). The rank value indicates an importance of a particular page. A hyperlink to a page counts as a vote of support. The PageRank of a page is defined recursively and depends on the number and PageRank metric of all pages that link to it ("incoming links"). A page that is linked to by many pages with high PageRank receives a high rank itself. If there are no links to a web page there is no support for that page.

Numerous academic papers concerning PageRank have been published since Page and Brin's original paper. In practice, the PageRank concept has proven to be vulnerable to manipulation, and extensive research has been devoted to identifying falsely inflated PageRank and ways to ignore links from documents with falsely inflated PageRank.

Other link-based ranking algorithms for Web pages include the HITS algorithm invented by Jon Kleinberg (used by Teoma and now Ask.com), the IBM CLEVER project, and the TrustRank algorithm.

PageRank as a website quality indicator

PageRank could be a good quality indicator assuming that most people link to valuable content and nobody links to useless pages. However paid links, mandatory links for providing software or services, link spamming and other means can persuade or force webmasters to link, at least temporarily, to any content. Spam filtering that is applied as a countermeasure is not directly tied to the website value that only human expert can estimate. As a result, PageRank is not necessarily a good indicator of the quality or value of the website. Along with the PageRank, Google uses over 200 other methods to optimize the search results.

So what is your PageRank?
Mine is 0. Sigh~