Cookie

Hei, bukan cookies seperti yang ada di atas, I mean the HTTP one. 

"A cookie, also known as an HTTP cookie, web cookie, or browser cookie, is usually a small piece of data sent from a website and stored in a user's web browser while a user is browsing a website. When the user browses the same website in the future, the data stored in the cookie can be retrieved by the website to notify the website of the user's previous activity.[1] Cookies were designed to be a reliable mechanism for websites to remember the
state of the website or activity the user had taken in the past. This can include clicking particular buttons, logging in, or a record of which pages were visited by the user even months or years ago." —Wikipedia


Itu berarti mereka dapat melacak dimanapun kita berada, em.. sebetulya tidak juga, sejauh ada tidaknya kode pelacak yang ditanam pada website. Eg: Google Analytics.
Merasa tidak enak? mungkin dua addons ini bisa dijadikan pilihan. (1) Disconnect / (2) Ghostery.

Image source : http://commons.wikimedia.org/wiki/File:Chocolate_Chip_Cookies_-_kimberlykv.jpg