Google arguably tracks more online users than any other entity. The Web search giant not only owns and runs the DoubleClick ad serving system but also partners with millions of sites to serve Google ads next to content.
In other words, Google has been following you for a while. But, in recent years, Google initiated a way for its users to see exactly how the site profiles them in order to target advertising. This is called Google Ad Preferences (www.google.com/ads/preferences). The site will show you the content categories Google has tagged you with.
It even lets you remove or add interest categories. You can also just opt-out altogether. Microsoft and Yahoo! offer similar capabilities. Yahoo! calls its tool Ad Interest Manager (info.yahoo.com/privacy/us/yahoo/opt_out/targeting/details.html). And Microsoft Advertising’s controls are located at choice.live.com/advertisement choice.