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Browser cookies have been around almost as long as the web. Invented by an engineer at Netscape in 1994, the method for keeping track of people's browsing activity started out as a way for e-commerce sites to store your purchases in a shopping cart and are now widely used. But researchers and regulators now think that the evolution of a more advanced type of cookie known, appropriately, as a "supercookie" poses some serious privacy concerns. Used on websites like Hulu and MSN, invasive new tracking techniques like supercookies track users every move, steal your browser history and feed the data to advertisers, largely undetected. And whereas regular cookies are easy to find and delete, supercookies and history-stealing software are almost impossible to get rid of.

Privacy advocates have been concerned about cookies for ages. While it's convenient for a site like Amazon to keep track of which books you've been shopping for, it's disconcerting for some users that websites save that information and often sold to advertisers. Cookies are stored in a common location and removing them is straightforward. Supercookies, however, are linked to Flash software and stored elsewhere on your computer. Even if you delete your regular cookies, the more resilient supercookies can restore the data. You can delete them--they typically have a *.sol file extension and can be found in the Flash directory--on your computer. To keep your supercookies off of your computer for good, follow these instructions.