Microsoft Corp announced that it has reached an agreement to acquire Greenfield Online Inc, owner of Ciao GmbH, one of Europe's leading price comparison, shopping and consumer reviews sites, in a move that will further extend Microsoft's search and e-commerce services in Europe. Under the terms of the agreement, Microsoft will commence a cash tender offer to purchase all of the outstanding shares of Greenfield Online for $17.50 (US) per share in a transaction valued at approximately $486 million (US).