#comment_nav > a:nth-child(4)  {
    position: fixed;
    right: 20px;
    bottom: 20px;
    cursor: pointer;
    padding: 10px 15px;
    background: #39f;
    border-radius: 5px;
    color: #fff;
    font-size: 15px;
    text-decoration: none;
}