It's part of a drive to get more Christians to go to church.
One billboard warns: "Keep using my name in vain and I'll make rush hour longer -- God."
Another asks: "What part of 'Thou shalt not ...' didn't you understand?"
The "God Speaks" campaign was created by Florida ad man Andy Smith and financed by a well-known South Floridian who wants to remain anonymous for now.
Smith won't say how much is being spent on the God Speaks ad effort. But he promises the whole story will be revealed later this month.