Which one are you talking about ? I think it's should be. I tried the first one, AdSense Notifier, but give it up. Don't earn enough to monitor it so closely.
haha, I stare at my notifier, literally, every few seconds my browser is on.. but just for curiousity, is there any other type of addon for FF??
It's really really convenient to just be able to glance at the corner of an Internet window (which I almost always have open) and see my earnings. Also by right clicking on that section where the stats are displayed, you can open up your AdSense account in a FireFox window or tab (I use the latter) so it saves me the trouble of logging in. Just please please PLEASE do NOT install it if you have a shared computer . That could be bad.
The problem is it will log in to give print your earnings all the time, does google care if you go in and chek your earning every minute ...?
The plug in actually checks every 20 minutes (Google recommended 15 - 25 minutes). Not every minute . So there is just a few minute delay.
Google Desktop also has got a Gadget to check your adsense revenue, but tbh it su*ks... Safe? I think so, but you're really never that safe.