.relative { position: relative } .absolute { position: absolute } .fixed { position: fixed } .top-0 { top: 0 } .right-0 { right: 0 } .bottom-0 { bottom: 0 } .left-0 { left: 0 } .z1 { z-index: 1 } .z2 { z-index: 2 } .z3 { z-index: 3 } .z4 { z-index: 4 } .absolute-center { top: 0; right: 0; bottom: 0; left: 0; margin: auto; display: table; }