Yahoo! Inc. (YHOO) is selling its HotJobs search site to rival Monster.com. (MWW).

The deal is worth $225 million in cash, according to multiple reports, and Yahoo! will get an undisclosed cut of revenue over the next three years by sending traffic to Monster.

Investors weren’t so keen on the idea, though. Yahoo! shares dropped a little more than 1 percent to $15.24 and Monster’s stock plummeted more than 19 percent to $13.29 by 12:45 p.m. Eastern.

Analysts, too, reacted with shock. Deutsche Bank analysts Jeetil Patel downgraded his rating on Monster from hold to sell. He said Monster overpaid for HotJobs and, fresh off disappointing fourth-quarter losses, will continue to see revenue fall in 2010.

Regulators have to approve the deal. If and when that happens, Monster will acquire relationships with 600 newspapers across the country that offer job postings through Yahoo!’s HotJobs board.

The news, announced on Wednesday, comes as Yahoo! CEO Carol Bartz works to turn the Internet company into a focused content provider. To do that, Bartz over the past year has cut hundreds of jobs, shuffled management and sold various Yahoo! assets.

Yahoo! bought HotJobs in 2002 – outbidding Monster.com, incidentally – for $436 million in stock and cash. This week’s sale to Monster comes as unemployment in the United States remains higher than 10 percent and as the Labor Department on Thursday reported a surprise jump in weekly unemployment claims.