/* back-to-top-button.css */
.back-to-top{width: 40px;    height: 40px;    position: fixed;    bottom: 2em;    right: 2em;    background: url(../../files/images/back_to_top_button.png) no-repeat;    opacity: 0.7;    z-index: 1000;    display: none}.back-to-top:hover{opacity: 0.9}