Google has just updated its advertising system to do “behavioral targeting”, in essence they track you as you move around the web and display ads that are targeted towards you based on what the perceive are your interests.
For instance if you visit a bunch of sports related sites then Google will determine that you are into sports and serve up sports related ads to you.
This is all done using tracking cookies and is built around the Doubleclick tracking infrastructure.
We use third-party advertising companies to serve ads when you visit our website. These companies may use information (not including your name, address, email address, or telephone number) about your visits to this and other websites in order to provide advertisements about goods and services of interest to you.
You are warned :)
More importantly what if you don’t want to be tracked ?
The preferences page is a particularly interesting, in that it shows you the “interest” areas that Google has derived based on your surfing habits. You can also manually add interest areas if you want!
My advice however is to just use a browser add-on such as Adblock Plus for Firefox and you will never have to worry about seeing those ads ever again (you will however disable the blocker for rabidgremlin.com, won’t you? )