.mypresta_scrollup {
    background: url("back-top.png") no-repeat scroll 50% 50% #333;
    bottom: 35px;
    display: none;
    height: 55px;
    position: fixed;
    right: 12px;
    width: 55px;
    z-index: 9999;
}
.mypresta_scrollup:hover { background-color: #2DB9DD;}