.btn-top {
    background-image: url('/Design/top.png');
    background-repeat: no-repeat;
    border: medium none;
    bottom: 6px;
    cursor: pointer;
    display: none;
    height: 41px;
    outline: medium none;
    padding: 0;
    position: fixed;
    right: 20px;
    width: 50px;
    z-index: 9999;
    border-radius: 21px;
    height: 49px;
    background-size: 100% 100%;
    opacity: 0.7;
}

.btn-top:hover {opacity:1}