Today, as they often do, grubhub sent me an email offering 20 percent off. I followed the link and saw a favorite Chinese restaurant participated. Allegedly, the 20 percent discount would be applied during checkout -- they gave me no code to use. I filled the cart and started to place the order, but you guessed it, no 20 percent off. After some chat negotiations, received another email with 20 percent off. This time, the discount appeared, but got a "this order cannot be processed" message. Not the first time something like this has happened to me with grubhub. They try to lure me in with a deal, then renege.