#page_top{
  position: fixed;
  z-index: 10;
  right: 0;
  bottom: -50px;
}
#page_top a{
  position: relative;
  display: block;
  text-decoration: none;
}
#page_top a::before{
  top: -5px;
  bottom: 0;
  right: 0;
  left: 0;
  margin: auto;
}