AKQA was first taken on by in January to develop an online strategy for the company on a three-month trial basis.
During that time it developed a trial ad across sites including MSN, Virgin.net, Handbag.com, Google and Ticketmaster.
The ads, in formats including banners with search functionality, interactive drop-down banners, skyscrapers and Tangozebra Overlayz, run with the same strapline, "Yell.com - for UK shops and services", that was used in the trial.
Ajaz Ahmed, chairman of AKQA, said: "We're pleased to have been appointed on a long-term basis by Yell.com. The performance of the initial test campaign proves that digital media has an important role to play in the acquisition of new customers."
The campaign is being rolled out across a number of selected sites that are used by the business community.
John Hayward, head of consumer communications at Yell, said: "We've had a very successful trial period and are looking forward to embarking on this new campaign. We feel the creative elements of the campaign will help successfully position Yell.com as the first port of call for anyone searching online for UK business information."
The strategy and online media planning and buying was handled by i-level.
Last week, marketing services company Experian bought Yell.com's direct marketing arm Yell data.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .