div#gmap {
    width: 100%;
    height: 400px; /* If you change this don't forget to change the crosshair position to match */
}
div#crosshair {
    position: absolute;
    top: 192px;
    height: 19px;
    width: 19px;
    left: 50%;
    margin-left: -8px;
    display: block;
    background: url(crosshair.gif);
    background-position: center center;
    background-repeat: no-repeat;
}