UPDATE: It turns out Pagerank is not dead after all. Google has simply updated the URL which is used to query it, which has caused various toolbars and websites to stop reporting the number. Dave Naylor spotted the update and has subsequently updated his own tool, which is now once again reporting PR accurately. The original article was as follows... If the words Search Engine Optimisation don't mean anything to you, look away now. Google appears to have disabled the display of PageRank on browser toolbars and online ranking checkers. Toolbar plugins, such as SEOQuake and SEOBook, which had been displaying the Google PageRank for the site being viewed are now showing as either N/A or 0. On Twitter, the majority of people in the industry rejoiced the seeming end of Google's Toolbar PageRank display. Since its first appearance several years ago it has been used, arguably more than it should have been, as a way of determining the quality of a website.
Scott_McLay: Well it looks like TBPR is dead - woohoo no more confusion over its importance
The PageRank which was visible on the Google Toolbar was always out-dated with that which Google actually used in their calculations for determining where sites should rank in the SERPs. The last confirmed roll-out of Toolbar PageRank was June 27th, 2011. Although many smaller updates had taken place, in particular for new websites and those which had been redirected from others. Presumably those who still made heavy use of PageRank - mostly link sellers or SEO agencies who didn't know better - will now presumably turn to MozRank, a website authority rating by SEOMoz. It may not be completely the end of the story for Toolbar PageRank, however, as some on Twitter reported they could still see PR.
KevStrong: To all the peeps saying that PR is showing as 0 - Mine works fine on Firefox 4.01 but my custom built PHP PR checker does not.