Many things typically come in threes, but it's rare to see three big acquisitions in one industry on a single day. But then again, wild deals -- rumored and real -- have dominated the online landscape for the last year and seem to be part of the web's very fabric.

At the top of today's heap stands CBS, which announced its $1.8 billion purchase of CNET Networks in a bid to expand its online presence. 

"Our idea is to have our content wherever, whenever you can get it, and adding CNET just makes that happen faster," CBS chairman Les Moonves said of the deal.

But CNET isn't without its fleas. The publisher, which was once renowned for its coverage of technology and the web, has taken a beating from blogs like TechCrunch.

Another company that has taken a beating -- Barry Diller's IAC/InterActiveCorp -- also made acquisition headlines today, though as a buyer.

IAC is reportedly paying $100 million in cash for Lexico, which owns Dictionary.com, Thesaurus.com and Reference.com.

The deal is expected to be a shot in the arm for Ask.com, IAC's cornerstone web property. The search engine, which ranks a distant fourth behind Google, has failed to push beyond 5 percent of total U.S. searches. By acquiring Lexico, IAC hopes to send the company's reference traffic back to Ask in order to help the search engine build brand awareness.

Meanwhile, Comcast upped its online presence with plans to buy contact management service Plaxo.

"We think the combination of Plaxo and Comcast together can supercharge both of our products," Sam Schwartz, executive VP of Comcast Interactive Media told The Associated Press. "Comcast is looking at Plaxo to become the social media backbone of its products."

Plaxo, which had been rumored to be a target of Google's earlier this year, is something of a curious choice for Comcast, which recently saw rival Cox Enterprises snap up an online ad network in the form of Adify.

Over the past few months, many have wondered as to the precise nature of Plaxo's business model. The company was once a social network, and then seemed to abandon that business in favor of contact management when it began losing users to MySpace, Facebook and LinkedIn.

In January, Plaxo made headlines with its decision to join the DataPortability Workgroup along with Google and Facebook. Data portability has become a big issue in the last few weeks with news that MySpace, Facebook and Google will all vie to become a digital hub where users can update and share their information across the entire web. While Plaxo will certainly be part of that fight, it's by no means the dominant player. However, its content management technology could mesh well with Comcast's ISP business.

Comcast did not disclose the price it paid for Plaxo.