From Their Website:
Priceline.com - Travel, airline tickets, cheap flights, hotels, hotel rooms, rental cars, car rental
* Priceline's Name Your Own Price® reservation service is different from fixed-price travel sites like Hotels.com and Expedia.com. With Priceline's Name Your Own Price® reservation service, the exact hotel is shown only after purchase. Name Your Own Price® Hotel examples shown are for offers booked between April 6 and April 23, 2007 for check-in between April 9, 2007 and July 4, 2007 and do not include applicable taxes and service fees. Percent savings shown above are as compared to the published prices shown on Hotels.com and Expedia.com for the same hotels and the same dates. There is no guarantee that hotels or prices will be available. Actual prices and availability are always subject to change. All prices and dates may not be available at time of travel booking and savings are not guaranteed.