$10 Off $100 Today, Plus $10 Off $50 on Future Purchase with MasterCard has $10 Off $100 Today, Plus $10 Off $50 Future Purchase using a MasterCard during checkout and applying coupon code 3TLRXE3N.  It is valid on 12/20 only.  Here is a screenshot for your reference.  Detailed terms and conditions are available here.  Note that this even works on Kindle Fire as well.