SAN FRANCISCO - Online advertising start-up OpenX and Microsoft Corp announced a partnership to promote each other's Internet technologies to their respective customers.

The deal will significantly expand the distribution of OpenX's technology for serving ads on websites, as the company seeks to boost its roster of large Web publishers, said CEO Tim Cadogan.

OpenX will also make it easier for its Web publisher customers to use Microsoft technology that analyzes the content of a Web page and matches relevant ads to the page.

Microsoft and OpenX did not disclose the financial terms of the multiyear deal, though there will be the opportunity for both companies to make money in the deal, said Peter MacDonald, Microsoft's director of advertising business development.

The deal marks the latest shift in the competitive landscape for ad serving technology, which allows Web publishers to manage ads across their sites.

OpenX competes with companies like Google Inc's DoubleClick and Microsoft's own aQuantive product.

MacDonald said that the OpenX ad server technology might be more appropriate for certain types of Web publishers.

While Microsoft only offers ad serving technology that is hosted in Microsoft's data centers, he noted that OpenX allows publishers to install the software on their own computers. OpenX technology is also open-source, allowing customers a wide degree of customization options.

MacDonald said the deal was not a sign that Microsoft was shifting its focus away from offering ad serving technology.

Microsoft acquired aQuantive in 2007 for roughly $6 billion. In August, Microsoft sold aQuantive's ad agency business, Razorfish, to Publicis for $530 million.

OpenX has more than 50 million Web publisher customers and runs more than 300 billion page impressions a month through its software. The company, which raised $10 million in funding in May, launched a separate online ad exchange marketplace earlier this year. (Reporting by Alexei Oreskovic; Editing by Gary Hill, Bernard Orr)