Google will, ironically, rely on tracking cookies to help users opt out of behavioral ads. The Chrome extension, which was , activates do-not-follow cookies from the , telling them not to track your behavior on the web.

Ad networks that participate in the NAI already allow you to opt out on , but these preferences are lost if you clear your browser's cookies. Keep My Opt Outs remembers your do-not-track preferences and adds new participants in the Network Advertising Initiative automatically.

Mozilla to Firefox's basic settings, instead of using a browser extension. When users visit a website, Firefox will broadcast the user's preferences as an HTTP header, effectively telling sites not to track users on a case-by-case basis.

Firefox's approach is cleaner on the user's end, but will take longer to implement. Even if Mozilla adds this feature in the next version of Firefox--not a given, a --websites will still have to recognize the HTTP header. For now, the cookie-based approach that Google is adopting will have to suffice.

Still, both approaches share the same flaw: . Although the Network Advertising Initiative consists of the 15 largest ad networks in the United States, unscrupulous advertisers in the web's shadier corners certainly won't be participating.