Overture provides keyword-linked pay-per-click advertising that appears when people run a search on Microsoft’s MSN web sites. The extension covers MSN properties internationally, in North America, Asia and Europe.

MSN is believed to account for a material percentage of Overture’s sales. Overture contributes to Yahoo’s marketing services revenue segment, which represented 84% of the company’s overall revenue in the last-reported quarter.

For this reason, these major deals are closely watched, particularly given the fact that Microsoft has vowed to catch up in the search market by bringing more of the technology in-house. MSN, for now, also uses a Yahoo-owned algorithmic search engine.