Editing Validation Error stating

45 	#column1 	Property opacity doesn't exist in CSS level 2.1 but
exists in [css3] : 0.75
57 	#column2 	Property opacity doesn't exist in CSS level 2.1 but
exists in [css3] : 0.75
69 	#column3 	Property opacity doesn't exist in CSS level 2.1 but
exists in [css3] : 0.75