A new article that discusses the rules for calculating the value of PR has been created by bobmutch. Of course, all PR calculators are basically guesstimates, but they can be helpful in determining the possible value a backlink will have to your page. Bobmutch uses Bob Wakfer's pagerank calculation chart as the basis of the article. Check out the new formula, or rules as bobmutch calls them, at http://www.seocompany.ca/pagerank/page-rank-calculation.html.