Ryan Paul writes:
One of the new features that Mozilla introduced in Firefox 4 is a Do Not Track (DNT) setting. When the user enables the DNT option in the browser’s preference dialog, Firefox will transmit a custom header in HTTP requests that will inform servers that the user wants to opt out of Internet tracking. The concept has obvious merit because it provides a simpler, more predictable, and more consistent approach than the cookie-based mechanisms that are currently used today to signify opt-out status.
Read more about who says they’ll honor DNT on Ars Technica.