You will be surprised how much time you spent on particular webpages.
If you want to know which sites you spend most time online, this extension will help you. It collect statistics about your site viewing time and show charts about it and:
Shows the time you browse this site today at extension icon;
Shows total time you browse;
Shows total statistics on the Pie diagram, maked by Google Chart Tools API;
You can share your statistics via Twitter or Google plus;
Show some detailed statistics on additional statistics page;
Show number of sites in every domain zone like .com or .ru.
timeStats is completely free and without any ads. It will not send your stats, if you do not want to.