Software giant Microsoft has started an exclusive deal to provide banner advertising and sponsored links for social networking website Facebook.
Microsoft says the deal should be attractive to advertisers
Details of the new agreement, which is expected to start running later this year, have yet to be released.
Microsoft said it thought the combination would be "incredibly attractive to advertisers".
Earlier in August another networking site, MySpace.com, joined forces with Google in an advertising deal.
Search engine Google is tipped to pay at least $900m (£475m) to share advertising revenue with MySpace.com, which belongs to NewsCorp's Fox Interactive Media.
The Microsoft and Facebook deal, which will use Microsoft's online advertising mechanism adcenter, is expected to last until mid-2009.
Founded as an online social directory by Mark Zuckerberg in 2004
7.5m people registered
Seventh most popular website in US
"Facebooking": checking someone's Facebook profile before meeting them
"Facebook official": really going out together
Microsoft started adcenter in May in an attempt to compete with search engines Google and Yahoo.
Both firms have seen their online advertising platforms generate strong revenues.
Facebook, which is the seventh most popular site in the US, has more than nine million registered users.