Near the bottom of your Cart, under the Product Total, see your savings.
Discount Coupons only
A.   Only 1 discount coupon per order.
Gift Cards only
A.   If your don't use the entire gift card, save the unused portion for a future order.
B.   If your Product Total is more than your gift card, you can pay the balance by credit card, PayPal, money order or check.
C.   You can use 1 coupon and gift cards for the same order. Type 1 code, click 'Redeem Code'. Repeat.