Web Bugs – Here Are the Rules
AKA web 'beacons'
Web bugs, aka web beacons, are single-pixel GIF image tags in HTML documents used to track web users. The invisible bugs allow the page owner to measure user activity based on image server logs.
The NAI rules, which represent the industry's attempt to self-regulate, ask companies using these techniques to provide a notice of web bug use that says what the bugs are used for and what data is transferred to third parties.
If the bug can be tied to personal data, such as via a cookie or an email address, and it will be disclosed to third parties, then there needs to be an opt-out for the user, but only when the disclosure is for purposes "unrelated" to the reason the data was collected.
Companies included in the development of the guidelines include IBM, Microsoft, the US Postal Service, DoubleClick, WebSideStory, Advertising.com, 24/7 RealMedia, Coremetrics, KeyLime Software and Guardent.