Google just ongoing tests a new tracking system that will present ads base on your web browsing history. The buzzwords for this are interest-based marketing, behavioral target and online behavioral targeting.

Goggle's introduction to the topic, Interest-based advertising: How it works doesn't sound startling or enveloping, but it may be the first pace down a greasy path.
The browsing times past that Google uses exists in cookies rather than the web browser cache. My previous posting, What are cookies?, provided an introduction to cookies.

When fellow Computerworld blogger Preston Gralla wrote How to protect yourself against Google ad questioning he argue the representative line from Google about how to opt out of their new profiling scheme. Over at PC World, JR Raphael enclosed the same subject in Google's Behavioral Ad Targeting: How to Reclaim Control.
That article has links to opt out pages for Google, Yahoo and Microsoft as well as a master opt out page for a whole host of promotion networks from the Network publicity Initiative.
But this type of opting out just sets more cookies. In the worst case, Google requires you fix browser plug-in software on the way to insure their opt-out cookie never gets deleted. Setting added cookies means you have to trust how these cookies are used. This is a Defensive Computing blog and trust is not part of suspicious Computing. So, I offer another approach. An approach to prevent the creation of cookies starts ad networks in the first place.

For now, I'm focusing on Internet Explorer 7. The good news is that IE7 users can easily block third party persistent cookies ,those also known as tracking cookies.