-The Like button, Tweet button, or Google buttons.
You've seen them on lots of websites and have probably used them to share pages or videos with others.
These buttons tell Facebook and Twitter what other sites you've been to and tie that information to your Facebook or Twitter account name and computer's internet address.
-They're embedding a piece of code in your browser so that that is tied to you and your user profile on their accounts,
and they know, then that way they can find out that this user visited these pages.
-Brian Kennish, founder of Disconnect, Inc., has researched this for the Wall Street Journal.
-So even if you don't interact with the button, even if you don't click it, Facebook will see that you are on that particular page.
-Here's how it works.
You go to Facebook, you log in, you spend some time there, and then, and this is key, you move on without logging out.
Let's say the next site you go to is New York Times.
Those buttons, without you clicking on them,
have just reported back to Facebook and Twitter that you went there and also your identity within those accounts.
Let's say you moved on to something like a site about depression.
This one also has a tweet button, a Google widget, and those, too, can report back who you are and that you went there.
-There are 700 million people that are logged into Facebook at any given time, so those people are actually transmitting the page that they're on as well as their name.
-Facebook, Twitter, and other widget makers including Google say they don't use this browsing data generated by their widgets to track you,
and they also claim to delete the data after anywhere between a couple of weeks or a few months.
-Just closing your browser, just turning off your computer doesn't-- it doesn't end these-- this tracking.
-Users need to stay aware of logging in and logging out.
For CBS News, I'm Brian Cooley, CNET.com, in San Francisco.
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