The CSS -webkit-backface-visibility Apple extension property determines whether or not a transformed element is visible when it is not facing the screen. Use this property to specify whether or not an element is visible when it is not facing the screen. For example, if the identity transform is set, an element faces the screen; otherwise, it may face away from the screen. For example, applying a rotation about y of 180 degrees in the absence of any other transformations causes an element to face away from the screen.