Yahoo has moved to further strengthen its service to advertisers by buying web marketing business BlueLithium for $300m (£149.4m).
Set up in 2004, BlueLithium provides technology enabling websites to better match adverts with users' interests.
The purchase is the latest in a series of deals by Yahoo as it seeks to regain ground on market leader Google in the web search sector.
In June, boss Terry Semel quit after concerns about the firm's direction.
Yahoo's profits have fallen in each of the past six quarters, prompting new boss Jerry Yang to start work on a "strategic plan" to improve the firm's performance.
He has sought to make Yahoo's web search functions more attractive to advertisers, recently buying online advertising exchange Right Media for $700m.
Mr Yang said the addition of BlueLithium, whose clients include General Motors, to the Yahoo stable would help Yahoo advertisers to maximise their online expenditure.
"BlueLithium's products, technology and team will be an integral part of our drive to build the industry's leading advertising network," he said.
BlueLithium, which specialises in analysing data on web usage, employs 145 staff at 10 locations in the US.
All the leading web search providers have been strengthening their advertising functions in recent months.
Microsoft bought aQuantive for $6bn last month while Google's $3.1bn acquisition of DoubleClick is awaiting clearance by US regulators.