It depends where you live--and it also depends on the fine print that you will find on the website, but all else being equal, the hotel has a contractual obligation to honor the rate quoted. If I were you, I would call the toll-free number for the chain and confirm that the conditions you agreed to when you confirmed the reservation on-line are reflected in their records. Barring any language in the terms and conditions on the website, it sounds to me like you have a binding contract.