(Editor's Note: Following publication of the initial version of this article, the Media Rating Council confirmed a 90-day waiting period before its "two-second" video viewability rule becomes official. See updated coverage here.)In a move that effectively establishes “viewable” impressions as the currency for online display and video advertising, the Media Rating Council today will lift an industry moratorium on the new metric. The move follows a period of review of the major third-party research supplier's methods for calculating “viewability,” establishing a standard for comparing data from various vendors regardless of the methods they use. Describing the new industry standard as a “common denominator in their viewability counts,” David Gunzerath, senior vice president-associate director of the MRC, said it was the result of a review of the disparate methods used by various vendors that “identified a half dozen reasons” why their viewability counts differ. The new MRC guidelines, he added, effectively “bring them into alignment.” The resolution paves the way for establishing a true GRP -- or gross rating point -- metric for comparing online advertising buys against other media, particularly television, as well as calculating online's contribution in cross-platform advertising campaigns and media buys. The new standard defines an online ad impression as being viewable if 50% of its pixels are viewable to a user for one continuous second for a static display ad, or two seconds for an online video ad. Gunzerath said the reasons for the differences emanate from the fact that various vendors have different reasons for calculating viewability and offering it as part of their solution. For example, some suppliers focus on “ad verification,” while others focus on audience estimates, and the differences in how and when they calculate viewability in their processes is what accounted for most of the differences. Now that the MRC has lifted its advisory and issued recommendations on how to process a common viewability metric Gunzerath said a flurry of announcements are likely to be issued by the major vendors supplying viewability data. The result, he said, will be that “digital advertising will be in a stronger place,” because the standard will improve the perceived quality of measurement in the eyes of advertisers and agencies versus the other major media they buy. “It opens the door for digital advertising to increase its share, particularly among [brand marketers],” Gunzerath predicted, adding, “We think this is a qualitative improvement that will certainly allow brand advertisers to better evaluate their campaigns.” Following the MRC's announcement, media audience measurement giant Nielsen announced a global deal to expand Integral Ad Science’s viewability data within Nielsen’s Online Campaign Ratings (OCR).