CSS z-index Property

The css z-index property controls the stacking order of elements. As the x-axis defines the horizontal (left-right) position of elements on the screen, and the y-axis defines the vertical (top-down) position, think of the z-axis as the third dimension or depth-of-field, rising “out of” the screen, towards the viewer, or descending “into” the screen, away from the viewer.

Syntax for z-index property

auto | integer | inherit