The Google PageRank Toolbar in SEO circles is a hotly debated item, as are most issues dealing with Google. Some say it's useless, others say it gives you a general overview of your site's standing in Google. Regardless of who is right, this Toolbar shouldn't be ignored nor worshipped, just closely watched.
The Google PR Toolbar is a simple tool you can download and place on your browser. When you surf the web, this toolbar will give you Google's PR or Page Rank for that particular site or page. Google ranks all web pages from a scale of 0 to 10. This Toolbar is more like the Richter scale than an ordinary scale, there's a big difference in the rankings as you go up and they are not proportional.