When you visit a website it knows the IP address of the network your using, a number like 123.654.355.33
This IP address is given a description, often by your ISP. Like comcast.321.miami
Google, when they went around with their street view vehicles, also mapped people's wifi networks and IP addresses along with their geographical locations. Which they got into a lot of trouble for in some countries as a result of being sneaky.
Not only that, web bugs and trackers on web pages gleam information, say a lot of people from a IP range of 123.000.000.01 - 123.000.000.45 always read the Homegrown Times, a online newspaper concerning the fictional town of Cocos Beach. It can be then inferred that a new person coming from a IP address of 123.000.000.34 is also from the town of Cocos Beach.
When you visit a web page, it contains advertising. The servers serving these ads don't place the ads directly on the server hosting the web page, they send them straight to your machine. Thus they have your IP address when your computer asks them for the ads.
The way your computer asks them for the ads is by instructions sent to you via the web page you visited.
So in order to defeat the geotracking, you have to have software installed that recognizes the request for the ads and blocks them.
Now it might be the ads are still getting through, but they are just not showing on the screen, because it's possible for web pages not to display the information you seek unless the they get a response from the ads or the ad server.
A constant war against marketeers and consumers is ongoing, the marketeers wanting to know every point and click a user does, and people wanting to maintain their privacy online.
If some young person is bi-curious, trying to determine if they are truly gay or not, might surf bi-sites to come to a understanding that's they are really straight after all. They surely don't want a record of that getting out or receiving gay oriented literature mailed to their house.
Now the trouble is Apple, with closed devices like iPads dependent upon a AppStore Apple controls, doesn't allow software to be installed to protect a users privacy online. All the web bugs, trackers, ads and so forth just operate at full speed. Not only that Apple ITSELF is in the advertising business.
Combined with the fact that SSD drives are NOT being completely erased, means someone with the skill and ability can take a iPad and dissect everything you have been doing with the device online.
If a young person took a innocent picture of themselves singing in the shower and didn't know to crop out certain parts, placed that photo on a iPad or iPhone or iPod Touch. There is no way to get it off the device without destroying it as they use SSD for storage.
It's a really sad day when the industry is out to take user control away from them, throwing in with the likes of marketeers and advertising companies like Google and now Apple too.
And people praise Chrome? Firefox is the browser for the people and their concerns, not Safari or Chrome.
And if you managed to get down to here, you need the following Firefox add-ons: NoScript, Ad Block Plus, Ghostery (delete Flash and Silverlight cookies in preferences!!), TrackMeNot, even BetterPrivacy. to maintain some sort of privacy online. Firefox has no defense against the dreaded Evercookie as of yet, but I'm sure it will have it in the next version of Firefox 4.0.