Because position: static
means “Ignore all the positioning instructions from left
, top
, z-index
, etc.”.
'z-index'
Value: auto | <integer> | inherit
Initial: auto
Applies to: positioned elements
— http://www.w3.org/TR/CSS21/visuren.html#z-index
An element is said to be positioned if its ‘position’ property has a value other than ‘static’.
— http://www.w3.org/TR/CSS21/visuren.html#positioned-element