.btntop {
  display: none;
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 10;
}
.btntop a {
  padding-top: 13px;
  padding-bottom: 14px;
  width: 48px;
  background: #000 no-repeat 14px 17px;
  color: #fff;
  font-weight: bold;
  display: block;
  text-align: center;
  border-radius: 3px;
  opacity: 0.5;
  filter: alpha(opacity=50);
  text-decoration: none;
}
.btntop .icon-btntop {
  font-size: 20px;
  font-size: 2rem;
}