CBS has entered into an agreement to acquire CNET Networks for $11.50/ share or $1.8 billion.

According to a company release, 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 approximately 200 million users worldwide.

San Francisco based CNET Networks owns sites including CNET, ZDNet, GameSpot.com, TV.com, mp3.com, CNET news.com, UrbanBaby, CHOW, Search.com, BNET, MySimon and TechRepublic.

CNet has had a troubled year that started with an attempt by a group of shareholders to take over the board, followed by large scale staff layoffs and even rumors of a possible investment by Google.

The $11.50 per share offer is a 45% premium on CNET’s closing share price of $7.95 Wednesday.