These days numerous advertisers follow people on the web by tracking their cookies.
These "cookies" are actually small text files, or logs, on your computer that show where you go on the web, what you do, buy and look for.
Advertisers use this log to sell you products and services that you've looked at in the past. That's why you often see the same ads for the same products on different web sites.
Not everyone appreciates this breach of privacy by corporations, so Mozilla has created Lightbeam, a new app for its Firefox browser that shows you who is tracking your cookies.
According to Mozilla:
When you activate Lightbeam and visit a website, sometimes called the first party, the add-on creates a real time visualization of all the third parties that are active on that page. The default visualization is called the Graph view. As you then browse to a second site, the add-on highlights the third parties that are also active there and shows which third parties have seen you at both sites.
After you install Lightbeam, go to "Tools" on your Firefox browser and click "Show Lightbeam" to see which third party sites are following you.
"It really is a stake in the ground designed to start a conversation about privacy," Mozilla's executive director Mark Surman told ZDnet.com.
"If you think about nutrition it's taken years of policy and public education about different types of food for people to be talk about a healthy diet," added Surman. "This is the same thing, this is saying 'Let's know a little bit more about what's happening' then we can get to discussions about what else is being tracked, to building tools to let you protect yourself, to education campaigns about how we want to protect about ourselves."
People can also go to the "Preferences" section of their Firefox browser, click the "Privacy" tab and choose not be tracked, but it is up to third party websites to obey.