The partnership will boost Nielsen Media Research's coverage to almost 600 websites.
Combining Nielsen//NetRatings' AdRelevance data with Nielsen Media Research's expenditure system, clients will be able to obtain improved information on adspend.
Nielsen Media Research plans to increase logs and gradually replace its estimated data.
The collaboration coincides with an increase in the amount of money spent on internet advertising.
The latest figures from Nielsen Media Research show that online display advertising spend accounted for nearly 3% of all media spend and was valued at 拢335.9m in 2005.
Paul Dunn, head of media insights at Nielsen, said: "This is a significant improvement on the information that Nielsen Media Research currently supplies.
"We will continue to work with the industry to further develop and improve our methodologies, especially in the area of search."
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