#page_top_btn{position:fixed;bottom:10px;right:10px;display:block;text-decoration:none;color:#fff;z-index:999;padding:8px 2px 0 2px;background:grey;width:35px;height:35px;font-weight:700;text-align:center;border-radius:50%;outline:0;opacity:0}#page_top_btn:hover{text-decoration:none;background:#000;color:#fff}