Is there any firefox plugin that lets me know how much time I spend on internet, categorized by sites, time etc

"1) MeeTimer

It records where you spend your time online.
It does it in a rather useful way, by allowing you to group websites into activities

2) TimeTracker

Features:

Tracks browsing time across sessions

Pauses automatically when you stop
browsing

Reset counter

Pause toggle per window

List 'work' sites that should not
count

Tooltip showing total time today,
since last reset and since installing.

Options Window"

"I think that pageaddict will do the trick

addons.mozilladotorg/en-US/firefox/addon/3685

But it seems it is only working with FF3.0"