The erstwhile J. Walter Thompson - now JWT - the oldest advertising agency in the U.S. (it's celebrating its 142nd anniversary), has purchased all the ad space on the Huffington Post homepage for one week, starting tomorrow, reports the New York Times. HuffPo will display nine of JWT's best TV commercials, with links for visitors to forward the spots via email or instant message. JWT is hoping the roadblock will result in a viral video outbreak, as well as add a veneer of hipness to its establishment image, according to the article.

JWT has teamed with HuffPo cofounder and viral media pioneer Jonah Peretti of Nike iD "sweatshop" sneaker fame. Peretti helped select the commercials that will run on the site, including spots for JetBlue, Levi's, Ford, HSBC and the Partnership for a Drug-Free America.

The one-week deal has likely cost JWT a sum in the low six figures, and the campaign is timed to run during the Cannes Lions International Advertising Festival, which begins in France on Sunday. HuffPo attracted nearly 1.2 million unique visitors in May, according to Nielsen/Net Ratings.