i might be wrong, but its hard to tell when all these companies write their terms and conditions in legalese:
Heres something from their site,
http://www.restaurant.com/about/terms#63. Restaurant.com Promotional Codes (referred to as "Promo Codes")
If you obtain a Promo Code that can be used to reduce the purchase price of a Restaurant.com Promotional Certificate, the additional following terms apply:
Unless otherwise specified, Promo Codes only apply to Restaurant Specific Certificates and Merchant Certificates, and not to Restaurant Gift Cards, Dinner of the Month or Double Deals purchases.
Promo Codes are based off the retail price of a Promotional Certificate as such price is posted on the Site at the time of purchase.
Promo Codes may not be applied to previously placed orders and cannot be combined with other promotions or offers.
We reserve the right to restrict particular Promotional Certificates to which you may apply Promo Codes at any time without notice, e.g. a Promo Code may not apply to all restaurants.
Promo Codes may not be applied when redeeming a Restaurant.com Gift Card.Promo Codes may or may not be applied automatically. You are fully responsible to review your order prior to submission to ensure that the order incorporates the Promo Code.