You know the drill. You're surfing online and find yourself on a clothing site, a cooking site, a real estate site or any other site that's selling you something.
After a bit, you decide you're done and continue surfing, only to find that ads for the site you left show up everywhere you look. It gets really annoying.
It's worse than advertisers just tracking you online though. They're building a personality profile that they can sell to other advertisers and third parties. So much for privacy.
The good news is that you can stop them.