#back-to-top {
    position: fixed;
    bottom: 40px;
    right: 40px;
    z-index: 99999999;
    color: #444;
    cursor: pointer;
    border: 0;
    border-radius: 50%;
    opacity: 0;
    width: 50px;
    height: 50px;
    transform:translate(0px, 400px);
    transition: 1s all ease;
    background-color: #ffffff;
    content: " ";
    font-size: 0px;
}

#back-to-top:after {
    display: block;
    margin: 17px auto 0 auto;
    content: '';
    background: url('../../image/sprite.png') no-repeat -103px -142px;
    width: 8px;
    height: 16px;
    transform: rotate(-90deg);
}

#back-to-top:hover {
    background: #575757;
}

#back-to-top.show {
    opacity: 0.5;
    transition: 1s all ease;
    transform:translate(0px, 0px);
}