Yahoo! today announced that it has entered into a definitive agreement to acquire substantially all of the assets of Tensa, more commonly known as IndexTools, a provider of Web analytics software for online marketing.

The acquisition includes IndexTools’ Web analytics business and technology as well as its Tensa R&D subsidiary. Upon completion of the acquisition, the addition of the IndexTools’ assets is intended to expand Yahoo!’s set of services designed to maximize its clients’ online marketing efforts.

The acquired technology is expected to extend Yahoo!’s current analytics offerings by adding capabilities to deliver relevant insights and metrics for online campaigns that run across the entire Yahoo! network. Following the acquisition, the first group of customers to benefit from these enhanced tools will be more than 150,000 small-to-medium businesses marketing on the Web with Yahoo!. Additional capabilities enabling third-party developers to monitor and optimize the traffic performance of their applications are expected to follow throughout the year following the acquisition.

The transaction is subject to customary closing conditions and is expected to be completed in the first half of 2008.