#backtotop {
  background:transparent;
  border: 0;
  bottom: 20px;
  cursor: pointer;
  display: none;
  height: 50px;
  position: fixed;
  right: 20px;
  text-indent: -9999px;
  width: 50px;
  z-index: 300;
  background-size: 50px;
}

#backtotop:hover {
  opacity: 0.8;
}

#backtotop:focus {
  opacity: 0.6;
  outline: none;
}

@media only screen and (max-width:991px){
/*@media (-webkit-min-device-pixel-ratio: 2),
(min-resolution: 192dpi) {*/
  #backtotop {
    background: url(/themes/custom/ed_online_books/images/back-to-top.png) no-repeat center center;
    background-size: 50px;
  }
}