Google pagerank tool bar its the best and for checking that its geniun or not just use it info:www.yoursite.com
I use the plugin but it seemed to cache the previous sites I visited and refuse to update when surfing new sites on so on, I would suggest not using it. Maybe just go to a page rank site for eg prchecker.info
Yeah, if the site has no PR it just shows the PR of the previous site you were on. I just find it convenient and unobtrusive (plus it updates quicker than a lot of the sites). I think there are probably more developed SEO Firefox extensions available (I just haven't got around to trying any of them out).
SEO For Firefox is the best in my opinion. All you do is right click on any website and choose SEO. It pops up a window of results. Here's what it shows for http://www.google.com.au :
I do check with prchecker.info for rankings. I will try SEO For Firefox today. Looks like pretty easy and quick. Thanks
ANother thing withy SEO for Firefox I only just discovered...you can enable it to show all links on any page that are "nofollow", so every "nofollow" link on a page is highlighted red...pretty cool eh!
checkpagerank.net works best for me and the other one which I use during PR update is digpagerank.com Digpagerank sums up information from all 45 data centers of google...
Google toolbar is an obvious choice. The FF seo plugin is a good one too. There are plugins for opera too.