Absolute horizontal & vertical centering block

main.css

.centered {
  position: absolute;
  top: 50%;
  left: 50%;
  text-align: center;
  z-index: 1;
  -webkit-transform: translate(-50%, -50%);
     -moz-transform: translate(-50%, -50%);
      -ms-transform: translate(-50%, -50%);
       -o-transform: translate(-50%, -50%);
          transform: translate(-50%, -50%);
}