Every day I see and analyze going on my website and found in several other websites that go down into PageRank 0 (PR0). This not only happens on my website but but also occur on many websites around the world. To monitor this PageRank I use Google tools and widget bar that is installed on every website.
With this zero PageRank (PR0), automatically all backlink or external links that have to be reset and I think Google periodically conduct inspections back to update the site every PageRank. Before PageRank reset (PR0), My blog technology got PR2 and now lost all external links. This blog is not regularly updated every weeks, a zero PageRank (PR0) after I change the new template and My blog regularly build backlink. It may be because the keywords that are not popular and less traffic.
My friend's blog is also experiencing the same thing from PageRank 2 (PR2) also be PageRank 0 (PR0). This blog is never backlink with another website, but got PR2. PageRank is difficult to measure and understand that only google problem. PageRank algorithm with the many things to consider and I think not only build backlink but how important backlink and keywords that are used to increase traffic from search engine Google.