#wallpaper {
    position: fixed;
    z-index: 0;
    height: 100%;
    top: 0;
    left: 0;
    right: 0;
    overflow: hidden;
}

#background_ad {
    position: absolute;
    top: 0;
    left: 50%;
    width: 1904px;
    margin: 0 0 0 -952px;
    height: 100%;
}