Source: http://lifehacker.com/5497377/pageaddict-charts-your-web-surfing-habits
Firefox: Tracking habits—whether you're tracking your spending, amount of sleep, or other personal metrics—is an excellent way to get a big picture of what's going on in your life. PageAddict tracks and charts your web browsing for your review.
PageAddict is a Firefox extension that sits in the background and quietly monitors every web site you visit. You can review the list at any time and apply tags to the types of sites you visit to categorize them as work, research, personal, games, email, or any other category that will help you visualize what constitutes your browsing time.
In addition to providing visual feedback on what you're browsing you can also, if you notice a particular time suck in your browsing history, restrict access to specific sites. Your restriction can take the form of minutes or an outright ban. Check out the full site at the link below for additional information and screenshots. PageAddict is free and works wherever Firefox does.