EMPLOYEE PERFORMED THE PRE-OPERATION INSPECTION & CLEANED THE FRONT WINDOWS. AS HE WAS IN THE PROCESS OF DESCENDING THE LADDER ON THE RT.SIDE OF THE MACHINE, HIS HAND SLIPPED OFF THE HANDRAIL & HE FELL BACKWARD TO THE GROUND, LANDING ON HIS BACK. EE HAD A FLASHLIGHT IN ONE HAND, NOT ALLOWING COMPLIANCE W/INSTRUCTIONS GIVEN ACCORDING TO .11011- USE OF LADDERS.