There are initiatives to stop or curb this free-for-all: currently, a bill to prohibit ad companies and other online businesses from tracking and sharing your personal information is being examined , and popular browsers like and have been experimenting with "Do Not Track" options within their respective applications. Unfortunately, as these strategies are still in early negotiation and beta, you'll still need to use multiple defenses for thorough protection.
: There are moves afoot to provide blanket protection from tracking-- and even . But until such measures acquire some muscle, you can opt out of the major tracking networks by visiting the Network Advertising Initiative's . This industry-run Website checks your system for tracking cookies from participating ad networks and allows you to opt-out from them one at a time or all at once. It does so by setting "do not track" cookies that many marketing networks respect. Remember to visit this site on every browser you use.
The next step is to block cookies from third-party and advertising sites. In Safari this is under Preferences > Security > Accept cookies. Click the radio box next to "Only from sites I visit" to protect yourself. In Firefox, go to the Privacy tab in Preferences, select Use Custom Settings For History from the Firefox Will drop-down, then deselect Accept Third-Party Cookies.
You can also use your browser's private browsing mode. Private browsing in Safari (under Safari > Private Browsing) isn't very effective since it still saves cookies. Firefox (Tools > Start Private Browsing) saves less, but still allows tracking for that session and doesn't stop tracking by IP address.
If you want to really browse under the radar, you'll need to install additional browser plugins. To start, I recommend and . These add-ons block most Internet ads and any embedded tracking. But they won't stop all tracking. To further bolster your defenses, install for Firefox, Safari, or Chrome; it blocks Web bugs, tracking tags, and other techniques for over 200 tracking companies.