#btn-to-top-of-page {
    display: none;
    position: fixed;
    bottom:20px;
    right: 15px;
    z-index: 99;
    font-size: 18px;
    border: solid 1px white;
    outline: none;
    background-color: #414141;
    opacity: 0.5;
    color: white;
    cursor: pointer;
    width:40px;
    height: 40px;
    border-radius: 4px;
}

#btn-to-top-of-page:hover {
    background-color: #ff8700;
}