Did you know that most of the web sites that you visit  contain Web bugs? Web bugs are not really bugs in the true sense. They are hidden scripts that track your behaviour and are used by the sites you visit to understand their own audience.

Ghostery is a free add-on for Firefox that can help you discover the hidden web bugs. Ghostery alerts you about the web bugs, ad networks and widgets on every page on the web. Ghostery searches the sites you visit for ‘Web bugs’ capable of quietly tracking your visits, and then alerts you to their presence. When the program discovers a Web bug, it displays a small pop-up naming what it found. If you’re at all interested in knowing how sites might track you on the Internet, you would like Ghostery.

You can configure how long the pop-up displays, and whether it appears at all. You can also choose to send statistics about the Web bugs you find for use in a GhostRank, which will contribute to a census of Web bugs across the Net. Of course, the statistics are anonymous and would not include your personal information.