...which sites you visit? If you think you do, you're right only up to a point. Sure, you decide which links to click on, but who decides which links appear on your screen when you keyword search in the first place? If you're searching with Google, Bing, or Yahoo, they use your previous searches, the websites you've visited and your IP address to tailor your search results. And if you're logged in to your gmail account while using Google, your Microsoft account while using Bing, or your Yahoo account while...(you get the idea) your search results may be even more selective. It may seem helpful, but it's also suffocating and limiting in terms of information access.
Moveon.org founder Eli Parser calls this tailoring of search results the "filter bubble."
If you want to learn more about the filter bubble, and why it's not a good thing, listen to this brief talk by Parser: