body{
background: #d3d3d3; /* Old browsers */
background: -moz-linear-gradient(top, #d3d3d3 0%, #ffffff 35%, #ffffff 65%, #d3d3d3 100%); /* FF3.6-15 */
background: -webkit-linear-gradient(top, #d3d3d3 0%,#ffffff 35%,#ffffff 65%,#d3d3d3 100%); /* Chrome10-25,Safari5.1-6 */
background: linear-gradient(to bottom, #d3d3d3 0%,#ffffff 35%,#ffffff 65%,#d3d3d3 100%); /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#d3d3d3', endColorstr='#d3d3d3',GradientType=0 ); /* IE6-9 */
}
.centered {
  position: fixed;
  top: 50%;
  left: 50%;
  /* bring your own prefixes */
  transform: translate(-50%, -50%);
}