#page-top {
    position: fixed;
    bottom: 20px;
    right: 20px;
}
#page-top a {
    background: #000;
    opacity: 0.5;
    color: #fff;
    width: 80px;
    padding: 20px 0;
    text-align: center;
    display: block;
    border-radius: 5px;
}
#page-top a:hover {
    background: #000;
    opacity: 0.4;
}