Google recently declined some of my ad groups because the display and destination URLs had different domain names. However, the two URLs lead users to the same landing page. The unfortunate side to this is that I received an e-mail from Google telling me that some of my ads had been declined one full day after I had added the ad groups. Therefore, those ad groups were turned off and I missed a full day’s worth of traffic.
The point of the story? Lesson 1: make sure your display and destination URLs are of the same root address; Lesson 2: check back frequently on any changes you make to your ad text or you could lose potential traffic.