DNT is an option in the major browsers that allows users to tell sites that they don t want their activities tracked as they move around the Web. Yahoo officials said the lack of an industry standard for DNT that s effective led to the decision. The EFF, one of the main proponents of the DNT system, is working on a new browser add-on called Privacy Badger, which is designed to prevent tracking from advertisers and others on the Web from advertisers.
Source: https://threatpost.com/yahoo-drops-support-for-do-not-track/105863/