div#site_header  h1 a {
    width: 640px;
    height: 192px;
    background-image: url(https://img.wiki3.jp/MrHFreeGameDojo/MrHFreeGameDojo3.png);
    background-size: 640px 192px;
    display: block;
    color: transparent;
    overflow: hidden;
}
div#site_header  h1 a:hover {
    color: transparent;
}