The web knows who you are. It knows which sites you like, what you search for and where you spend your time. By collating these and other bits of data, it's not hard to figure out quite a bit about you.
If that makes you nervous, you need to learn how to get rid of cookies and browse privately, without leaving a digital fingerprint everywhere you go. Click on Delete Browser Cookies for information on how to Get Rid of Cookies, Keep Cookies out of Your Browser and more.