When you’re surfing the net, every website you visit knows where you live. Sites can learn an amazing amount of information about you. Much of the time you may not care, but there are those occasions when you'd rather keep your identity cloaked. There's a lot you can do to browse the web without revealing your personal details.
What sites can learn
Every website you visit knows your IP address – the Internet address of your computer. Without that information the servers wouldn't know where to send the pages requested by your browser. Sites like What Is My IP will even report back that IP address, in case you need to know for yourself.
Given the IP address, a site can look up the geographic location of the server hosting that address and thereby learn approximately where you live. It's not always accurate, though. For example, when I'm connected through a Virtual Private Network (VPN) in London, websites think that's where I'm located. Still, some sites use this information to send locale-targeted ads.
Cookies for memory
A simple HTML-based website lives with short-term memory loss. When your browser requests a specific page or object, the server responds and promptly forgets about you. Next time your browser requests a page, it's a completely new interaction.
Ad networks are big consumers of cookies. The same ad network may place banners on hundreds of different sites. A cookie associated with the ad network identifies which ads you've seen most recently, so you'll get a different ad from the rotation each time. The ad network can also build up a dossier on your habits by noting the ad-equipped sites you visit, the site you linked from, ads you actually click, and more.
The cookie cure
Wiping out all stored cookies and preventing sites from storing new cookies would, of course, eliminate any possible privacy loss through cookies. That's a bit extreme, though. Some sites can't even function with cookies disabled. But do consider going into your browser's settings and disabling "third-party cookies." This prevents ad networks from using cookies to track you.
Become truly anonymous
Surfing without giving away anything about yourself can be simple. Google the words "free secure anonymising proxy" (no quotes) and experiment with the sites that turn up. A secure anonymising proxy sits between your browser and the sites you visit. The site sees only the proxy.
For a more thorough solution, download and use The Onion Router (TOR). This open source tool was born as a US Navy project, but now it's used by all kinds of people worldwide, including the hacktivist group Anonymous.
When you surf through TOR, your browser's data requests take a circuitous route through randomly-chosen TOR servers. All traffic is encrypted except the final connection from a TOR server to the actual website. Anyone intercepting a packet along the way won't learn anything about you or the destination website.
If you're a journalist travelling in a country that limits Internet access, connecting anonymously may be a matter of life and death. The TOR network is easy to use and provides excellent cover. For occasional forays into anonymous surfing a free secure anonymising proxy website may be sufficient. But for idle web surfing, the anonymity of the crowd is probably all you need. Yes, you're special, but so are the other millions of casual web surfers.