Establishing Stacking Order with z-index

Examples are from CSS Positioning by Eric A. Meyer

First (z-index: 8)

Second (z-index: 4)

Third (z-index: 1)

Fourth (z-index: 0)

Local Stacking Contexts

Elements with a z-order create a stacking order for their descendents.
Children are always in front of their parents

[one] (z-index: 3) [one] em (100)

[two] (z-index: 10) [two] em (10)

[three] (z-index: 8) [three] em (-343)