ImageIt seems that beta streak of Firefox 4 will never end, however at least beta 11 brought the new "Do Not Track" function which aims to provide increased privacy. After activating it from the Advanced windows in Options, the function will send a header "telling" websites that you want to opt-out of third party, advertising-based tracking.

The advantages to the header technique are that it is less complex and simple to locate and use, it is more persistent than cookie-based solutions, and it doesn’t rely on user’s finding and loading lists of ad networks and advertisers to work. To test out the new feature, get the Firefox 4 beta 11 from here.