Throwing down a challenge to the rest of the industry, Millennial Media (NYSE: MM) has signed up with Integral Ad Science to provide its clients with what it calls "a 100% viewability guarantee" for in-app mobile advertising campaigns.

The move is a demonstration that quantity has now been overtaken by the quality of the mobile advertising experience.

Clarity

Viewability, or ensuring clients don't pay for an ad a consumer might not have an opportunity to see, is one of these quality factors, alongside related issues such as brand safety and fraud.

"We are committed to becoming the largest mobile marketplace that provides 100% viewable, brand safe, and fraud free impressions," commented Millennial Media's CEO Michael Barrett.

Integral Ad Science completed an audit of the Millennial network this spring and both companies have been working with publishers on technical changes that improve viewability.