If you are interested in stats about your general surfing habits then page addict might come in handy. This firefox extension records the time that you visited a website and displays some nice graphs showing the dates, the minutes you have been on those sites and the total amount of minutes that you were using firefox on that day. That is of course not everything: You may tag a site or more than one site and check the stats of those tags as well. If you visit cnn, bbc and yahoo for work you could tag them “work” and receive the exact amount of time that you visited those sites.