Why does my headlight warning dinging turn on while im driving ?

i drive a 1998 ford mustang, and when im driving at night with the lights on, the dinging turns on. Im just wondering why it does it, and how i can get it to stop.Why does my headlight warning dinging turn on while im driving ?pull in front of a window and check lights ,brights and dims turn signal and running lights then back into same spot and do it for tail lights, turn signals in rear. you probably have one out and its letting you know.Why does my headlight warning dinging turn on while im driving ?It might be for the headlights but it could be a bad door switch, they all use the same alarm.