Dell laptop plasma screen needs cleaning?

My dell laptop screen has got finger marks on it - thanks to a zealous over active grand-daughter ! i am scared to use anything like a detergent or solvent spirit on it so somebody please help. i can find nothing in the dell manual that covers this.just for the record my dell is an inspiron 6000, i have had it a year and i am absolutely chuffed with it
Answer
I spray windex on a cloth and clean it. saw my computer guy do it and he said it was fine. good luck.