Web surfers who opt-out of targeted ads may still see the same irrelevant ad repeated as a result of not being tracked.

While it seems obvious that “Do Not Track” means “don’t store any data about the pages I visit,” representatives from the World Wide Web Consortium (W3C) have a different view. In a three-day meeting prior to a Senate Commerce Committee hearing on June 28, the group discussed possible exceptions that would allow for some data collection even if a user opts to not be tracked.

For instance, the W3C supports “frequency capping.” That means that even if you have activated DNT, advertisers could still track you enough to prevent you from seeing the same ad over and over.

But advertising industry representatives warn that being inundated with the same ad could be one of the unexpected and annoying results for DNT users. [Reality Check: State of 'Do Not Track']

The industry insists its voluntary measures are working. In his testimony before the Senate committee, Bob Liodice, president and CEO of the Association of National Advertisers, said one trillion ads are served each month with the Interactive Advertising Bureau’s alert icon that signals consumers that they’re being tracked and links to a DNT option. And, 1 million people have implemented a DNT option, such as the one offered by Mozilla in its Firefox browser.

But the DNT option adopted by those million Internet users has been largely ignored. Twitter is one of the few big companies that announced it responds to DNT signals. Facebook, however, does not. Microsoft said it will, but does not yet have a program to recognize DNT signals.

The effects of DNT can’t be measured until sites actually stop tracking visitors, but whether that really means no tracking at all, or just a little tracking, remains to be seen. The completed DNT package is expected by the end of this year.

Image courtesy of iStockphoto, barisonal