Cookies are small text files sent to your PC by servers at the websites you visit. They get their name from “magic cookies” in Unix, which are short data communications between two programs where the second program, the one receiving the cookie, may not even be aware of the content of the message.
In a similar way, web browser users are not usually aware of the content of the message in a cookie.
By convention, cookies are only sent from your computer to the domains that set them. An organization like Google or Yahoo, for example, would have many different destinations within their domain. Thus, many locations within the domain could interact with the cookie.
When you visit a website, you may encounter a graphic or other page element that actually isn’t part of the page. Instead, it’s served from a remote server. Your browser, in the act of connecting to that other location, gives that server access to their cookie.
An advertiser may recognize that cookie, identify you by habit (or name, if you’ve entered your name at some website within their sphere) and then decide what advertising to send to that page. All this happens as the page loads. This type of cookie is called a third-party tracking cookie. Generally, any cookie that does not originate in the domain you’re visiting is a third-party cookie. The advertiser would say that they are targeting ads that will likely appeal to you.
It doesn’t have to be a graphic, video, music link, or anything that you’ll recognize, either. It can be a single pixel in the corner of the page. These are called “web bugs.” A web bug may do nothing other than tell the advertiser, “He was here.”
Now multiply that by a million websites. A company that also sells ads would have a big incentive to make carrying their ads dependent on also carrying their tracking and targeting applications. This is called analytics.
Let’s look at getting rid of them.
