html, body, .wrapper-outer, .wrapper-inner, a {
  height: 100%;
}

body {
  background: #000;
}

.wrapper-outer {
   display: table;
   width: 100%;
}

.wrapper-inner {
   display: table-cell;
   text-align: center;
   vertical-align: middle;
}

img {
  width: 100%;
}