My cd player (deck) wont turn off in my car.?

i have a 04 ford explore and i installed the deck about 5 months ago. today when io went out to my car i realized the deck was still on. it was never like this i have a jvc head unit and i don't no how it would just do this all of the sudden. i have not taken the deck out or played with anything. can some one please help me.