Pricing was not disclosed. MonsterCommerce will keep its name, location and staff, and operate as a fully owned subsidiary, said Champ Mitchell, CEO of NSI, in an interview.

While NSI provides hosting services, it has been using a third-party e-commerce technology that "hasn't been a good experience for customers," Mitchell said. By purchasing MonsterCommerce, NSI will have the ability to influence the product road map for the e-commerce software and better serve the e-commerce needs of customers, he said.

NSI, founded 26 years ago, has 3.9 million customers, of which about 3.4 million are small businesses. Half of NSI's customers sell products or services online, he said.

MonsterCommerce has about 90 employees, all whom have agreed to stay on following the acquisition, he said. NSI, based in Herndon, Va., has about 670 employees.

MonsterCommerce will continue to support its own base of about 5,000 customers separate from the new NSI customers it will support. In addition to e-commerce functions for display and online billing, MonsterCommerce provides search engine optimization, online marketing and a service that builds Web sites for small businesses.