Microsoft today took another step in its strategy to beef up Live Search versus Google and Yahoo, unveiling a complicated deal to buy Greenfield Online and its subsidiary Caio, a European-based online price comparison and shopping site.

Under the agreement, Microsoft is offering $486 million for Greenfield. But in a related move, Microsoft today claimed to have secured a buyer for Greenfield Online's Internet survey solutions, the business that forms the heart of Greenfield Online.

Just last week, media firm Quadrangle offered about $426 million for Greenfield Online, a fact which raises the distinct possibility that Quadrangle is the mystery buyer of Greenfield's Internet survey arm.

The acquisition of Caio -- a property that Microsoft intends to keep -- is expected to bring new merchant customers along with new technology to Microsoft.

Consistently ranking a distant third in analyst ratings of the online search and ad markets, Microsoft has been using buyouts and a variety of other mechanisms in concerted attempts to catch up to industry leader Google and runner-up Yahoo.

In June, the numbers of searches on Microsoft's sites leaped 15%, according to comScore's numbers, during a month when Microsoft conducted a massive ad campaign for its Windows Live Search Club games and Windows Live Search Cashback Program.

Earlier in August, Microsoft reportedly named Jeff Kelisky -- inherited through Microsoft's recent acquisition of Multimap -- to be general manager of a new business unit tying together MSN's shopping site, Cashback, and other search-related entities.

Cashback -- a discount program for shoppers who buy products spurred by Live Search searches -- entered beta in May.

As of June, 680 merchants and 200,000 registered users were already using Cashback, said Colleen Healy, director of investor relations, during a conference call with analysts that month.

Also during the call, Microsoft CFO Christopher Liddell acknowledged that Microsoft is pouring more of its financial resources into online services.

"We've increased organic investments in operating expenses, driven in particular by a deliberate decision to invest more aggressively in our online services strategy," Liddell said.

Although Microsoft's bid to buy Yahoo failed resoundingly earlier this year, the company has been busily buying up many smaller players in the search and advertising space. In recent months, for instance, Microsoft closed the acquisitions of FairCast, a vendor with technology to help in the purchase of online tickets at low prices, and Navic Networks, which develops tools for delivering targeted ads to TV set-top boxes.

Industry observers have differed sharply, however, over whether Microsoft should keep spending so much of its money on search, advertising, and other aspects of online services.