Zed, the digital division of ZenithOptimedia, will work on sites including , , and .
The agency is briefed with raising traffic at the sites by 20% next year. CondeNet currently receives more than 32m page impressions a month and has 1.5m unique users.
It is the first agency CondeNet has appointed since M&C Saatchi created an advertising campaign for Vogue.com in 2000. The poster campaign, which showed a woman's nipple representing the dot in Vogue.com, won a number of awards.
Sue Douglas, president of new business at CondeNet, said: "As our magazine websites have grown and prospered, we have sought a partner to help us drive traffic and appeal to a wider audience. Zed Media has huge experience and contacts and impressed us with its imagination and practical ideas."
Conde Nast is also due to launch an expanded version of , following the recent launch of a more extensive US site.
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