#goto_top {
    position: fixed;
    right: 10%;
    bottom: 10%;
}

#goto_top a {
    width: 100px;
    height: 100px;
    border-radius: 20px;
    background: #65C8FF;
    display: block;
    color: #fff;
    text-align: center;
    line-height: 100px;
    text-decoration: none;
    font-weight: bold;
    opacity: 0.8;
}