Google Page Rank (PR) is an indication of a page's importance to the Google folks according to their mystical and ever changing algorithms. Still it does give an indication of how your site is doing in relation to other sites on the internet.

The Alexa toolbar is also another tool that some marketers use to gauge the popularity of their site in relation to other site. (As I understand it, it depends on other visitors with the toolbar installed in their browser who then visit your site - so how accurate or useful it really is, is a matter for debate).

Still it is interesting to have these gauges available and one of the reasons that I haven't been that fond of Firefox (apart from the fact that it broke some of my page layout at times) was that there was no toolbar for Google PR or Alexa ranking.

Well that is no longer a reason not to give Firefox another run.

You can pick up the Google extensions from http://quirk.co.za/searchstatus/. You will need to go there with Firefox so you can install right from the page.

Enjoy :)