Some super cookies live in the cache, which is where the browser stores Web pages you've visited recently. By clearing the cache, you'll get rid of them. That works, but there are two caveats: Dumping the cache will slow down your browser. That's because cached Web sites load right away; without the cache the browser has to render them from scratch. And when you visit that site again, a new super cookie will glom on to your browser.

Clearing the cache is easy: In Firefox, go to "tools," then "clear recent history." In Internet Explorer 9, go to "tools" and "safety," then "delete browsing history." In Chrome, go to settings and then "under the hood." Then click "clear browsing data."

But remember. We're talking arms race here. The UC Berkeley report also talks about a nasty technique called "respawning," which means just what it sounds like: The cookie recreates itself. These are hard to defeat. One way is to block any caching at all, but as I mentioned, not having a cache will slow your browser down.

There are two Firefox add-ons that are probably helpful, but I haven't had a chance to try them yet. One is called SafeCache, which doesn't yet work with Firefox 6 and RequestPolicy, which does work with Firefox 6.

RequestPolicy blocks what are called "cross-site requests," which means that a site you're visiting requests data about a site you've visited in the past. That's important information for advertisers and for Web sites that want to know where people are coming from.