#topcontrol {
    background: url("gotop.png") no-repeat 0 0px;
    height: 40px;
    width: 40px;
    z-index: 99999;
}

#topcontrol:hover {
    background-position: 0px -40px;
}

.top {position: fixed; bottom: 10px; right: 10px; cursor: pointer; opacity: 0;}
.top:hover {position: fixed; bottom: 10px; right: 10px; cursor: pointer; opacity: 1;}