body {
   margin: 50px; 
   background-color: #000000;
}
#main {
   position: absolute;
   top: 0;
   right: 0;
   bottom: 0;
   left: 0;
   text-align: center;
   height: 50%;
   margin: auto;
}
#main img {
   border: 0px;
}