In a new Google Webmaster video, Google's Matt Cutts, answering to the following quoted question:
"I use the Google Toolbar to monitor PageRank. I read on the Internet that it gives old and quite unreliable data. Can I have reliable realtime PageRank information about the sites I administer? And how can I identify causes of a PageRank drop?" silviot, Torino, Italy
Cutts offer the following reason for the PageRank drop:
- You lose a link from a third party page that had a lot of high PageRank.
- You have weird canonicalization issues with your site and domains that caused confusion.
- Or, at the most, because the site is selling links and thus Google will demote the PageRank of that site in order to remove the incentive from link buyers to purchase links from that site.
Watch the Cutts explains the PageRank drop in the video embedded below: