Set div at center of the screen CSS.

If you know the dimensions of div.

.centered {
  position: fixed;  /*IE6 position:absolute */
  top: 50%;
  left: 50%;
  margin-top: -50px; /* Half of the Height of div*/
  margin-left: -100px; /* Half of the Width of div*/
}

If you Don't know the dimensions of div.

.centered {
  position: fixed; /*IE6 position:absolute */
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}