Urgency is something that websites try to establish by advertising special promotional offers that are only good for a limited amount of time. The fact that the offer is so good and it does not last long creates an urgency in the buyer to go on the site and effect the purchase. This is an advertising ploy that is used to induce buyers to increase the speed at which they make their purchase. It can also be good to make a buyer actually buy something that they would otherwise have not bought due to the sense of a discount that is only good for a limited time.