StumbleUpon is a Web browser plugin that allows its users to iscover and rate Web pages, photos, and videos. Web pages are presented when the user clicks the "Stumble!" button on the browser's toolbar. StumbleUpon chooses which new Web page to display based on the user's ratings of previous pages, ratings by his/her friends, and by the ratings of users with similar interests. I.e., it is a recommendation system which uses peer and social-networking principles. There is also one-click blogging built in as well. Users can rate, or choose not to rate, any Web page with a thumbs up or thumbs down, and clicking the Stumble button resembles "channel-surfing" the Web. Toolbar versions exist for Firefox, Mozilla Application Suite and Internet Explorer, but also works with some independent Mozilla-based browsers.