#back-top a{
    display:none;
    position:fixed;
    bottom:20px;
    right:20px;
    border:2px solid #ffffff;
    background-color:transparent;
    width:40px;height:40px;
    line-height:36px;
    text-align:center;
    font-size:24px;
    z-index:100;
    color:#ffffff;
    transition:all 0.5s ease
}