http://mozdev.i2p/en-US/docs/Web/CSS/transform-function/translateZ
Note: translateZ(tz) is equivalent to translate3d(0, 0, tz) . Syntax css translateZ(tz) Values tz A <length> representing the z-component of the translating vector [0, 0, tz]. In Cartesian coordinate system it represents shift along z-axis. A positive value moves the element towards the viewer, and a negative value farther away.