CBS has agreed to acquire CNET Networks in a deal valued at $1.8 billion, the companies said Thursday. The purchase price comes to $11.50 per share, representing a 44 percent premium over Wednesday's closing price of $7.95. The acquisition will make CBS one of the 10 most popular Internet companies in the United States, with a combined 54 million unique users per month, and about 200 million users worldwide, the companies said.

The deal is expected to close in the third quarter. CNET's board has unanimously approved the deal, the company said.

Based in San Francisco, CNET Networks-owned sites include CNET, ZDNet, GameSpot, TV.com, MP3.com, CNET News.com, UrbanBaby, CHOW, Search.com, BNET, MySimon, and TechRepublic.

CNET Networks, News.com's publisher, recently announced a partnership with Yahoo to provide technology news and reviews to the search company. The companies also agreed to allow Yahoo to sell display ads on CNET properties and for CNET to sell ads alongside the content it provides on Yahoo sites.

CNET has been involved in a fight over control of its board with Jana Partners.