"Value proposition" clearly refers to the trade-offs -- users must accept the targeted ads as the price for receiving free software, services and content -- that advertisers say make the Internet what it is. As far as advertisers are concerned, tracking is required to provide targeted ads.

A group composed of advertisers, browser makers, privacy advocates and others have not finalized a DNT standard, even after months of intensive work. The Worldwide Web Consortium (W3C) standards-setting group has, however, preliminarily ruled that browser makers cannot set the DNT signal for users, essentially letting each website decide whether it will acknowledge or ignore IE10's.

Advertisers recently turned up the rhetoric about DNT. Earlier this month, the Association of National Advertisers (ANA), an industry lobbying group, said Microsoft's decision would "harm consumers, hurt competition, and undermine American innovation," and

Privacy advocates countered, saying that the ANA's demands were "bizarre."

Yahoo's decision to ignore IE10's DNT signal is notable because the California company is allied with Microsoft in search. In 2010, the two firms whereby Yahoo's search results are fueled by Microsoft's Bing search engine.