#backtotop {
  background: url(../button-top.jpg) no-repeat center center;
  cursor: pointer;
  display: none;
  bottom:10px;
  width: 40px;
  height: 40px;
  position: fixed;
  right: 10px;
  text-indent:-9999px;
  width: 40px;
  z-index: 999;
  opacity: 0.5;
}

#backtotop:hover {
  background: url(../button-top-o.jpg) no-repeat center center;
   -moz-transition: all 0.3s ease-out 0s;
   -webkit-transition: all 0.3s ease-out 0s;
   -o-transition: all 0.3s ease-out 0s;
   opacity: 1;
}

@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
  #backtotop {
    background: url(../button-top-o.jpg) no-repeat center center;
    background-size: 50px 50px;
  }
}

@media print {
  #backtotop {
    visibility: hidden;
  }
}