.stts-scroll {
    position: fixed;
    bottom: 40px;
    width: 40px;
    height: 40px;
    line-height: 40px;
    text-align: center;
    font-size: 25px;
    z-index: 99999999999999 !important;
    color: #fff;
    text-decoration: none;
    opacity: 0;
    visibility: hidden;
}

.stts-scroll.show {
    opacity: 1;
    visibility: visible;
}