body {
    background-image: url("https://images.cnblogs.com/cnblogs_com/aolia/1577072/o_191105064357204642-156423160243d3.jpg");
    background-repeat: no-repeat;
    margin: 0;
    color: #FFFFFF;
    font-size: 12px;
    line-height: 22px;
    font-style: normal;
    line-height: 150%;
}
div#div1{
    position:fixed;
    top:0;
    left:0;
    bottom:0;
    right:0;
    z-index:-1;
}
div#div1 > img {
    height:100%;
    width:100%;
    border:0;
}