Dirty marks appear easily on the iPad screen
Step 1 Unplug all cables and turn iPad off (press and hold the sleep / wake button, and then slide the onscreen slider) . Gather your supplies - soft lint free cloth and water.
Wipe the slightly damp cloth over the screen. Avoid getting moisture in openings ( around speakers and buttons).
DO NOT use window cleaner or other household cleaning products on the iPad screen. The iPad has an oleophobic coating on the screen to repel fingerprints - these products will destroy the coating.
Approved computer monitor cleaning liquids can be used on iPad's with screen protectors .