.back-to-top {
    position: fixed;
    bottom: 50px;
    right: 50px;
    width: 50px;
    height: 50px;
    box-shadow: 1px 1px 1px gray;
    text-align: center;
    border-radius: 50%;
    -webkit-border-radius: 50%;
    -moz-border-radius: 50%;
    -ms-border-radius: 50%;
    -o-border-radius: 50%;
}

.back-to-top i {
    line-height: 50px;
    color: #666;
    font-size: 20px;
    cursor: pointer;
}

.back-to-top:hover {
    box-shadow: 1px 1px 1px gray;
}