The process by which a sale is documented through the exchange of quotations, purchase orders, and sales confirmations is known in the courts as the "battle of the forms." Prior to the adoption of the Uniform Commercial Code (which with only minor variations governs the sale of goods in most states), the exchange of forms with contrary terms many times resulted in no contract being created. Now, in most circumstances, there will be a contract, but its terms may be supplied by reference to the Uniform Commercial Code and may not be what either party intended.  Careful attention is required to ensure that the contract you meant to sign is the one you actually have.