When you visit a Web page, what gets displayed on your screen can be the combination of the resources of many servers: a YouTube video hosted by Google, an image hosted on Flickr, and text content hosted by WordPress can be the building blocks of a single page. Another one of those building blocks is often advertising.
By default on some browsers (but luckily, fewer and fewer newer ones!) each resource has an opportunity to store a cookie on your computer. Cookies are harmless in themselves — just a small amount of text stored by the server — but when a particular resource is hosted on multiple domains, the resource owner, using cookies, can hold a list of your visits to those domains, effectively tracking you as you go between Web sites that show the same ads. Some advertisers have such a strong hold on the market (Google, for example), that they are a part of a sizable portion of the Internet and develop a clear picture — too clear — of who you are.
The solution is a setting in most Web browsers that allows you to let cookies from the main resource (the server whose address is in the address bar) through, which is required for many Web sites to work, while not allowing servers of embedded resources (such as an ad provider) to live on your computer, which is required pretty much only to track you. Here’s how to do it in all major browsers.
This is one of a 30-part series, “No Surveillance State Month,” where daily for the month of June I’ll be posting ways to avoid invasion of your privacy in the digital age. The intent of these posts is not to enable one to escape detection while engaging in criminal activity — there’s still the old-fashioned “send a detective to watch you” for which these posts will not help. Rather, this series will help you to opt-out of the en masse collection of data by the government and large corporations that places Americans in databases without their knowing and freely-given consent for indefinite time periods. We all have the right to privacy, and I hope you demand it.