html { 
  background: url(../image/background.png) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

#body_text {
  font-family:calibri;
  font-size:24px;
  color:#a3a3a3;
  text-align:center;
  width: 100%;
  position: absolute;
  top: 55%;
  -webkit-transform: translateY(-50%);
  -ms-transform: translateY(-50%);
  transform: translateY(-50%);
}