#scroll_top {
  z-index:1000000000;
    position:fixed;
    right:10px;
    bottom:10px;
    cursor:pointer;
    width:50px;
    height:50px;
    background-color:#3498db;
    text-indent:-9999px;
    display:none;

}
#scroll_top span {
    position:absolute;
    top:50%;
    left:50%;
    margin-left:-8px;
    margin-top:-12px;
    height:0;
    width:0;
    border:8px solid transparent;

}