body{
    background-image: url("https://images.cnblogs.com/cnblogs_com/CatdeXin/1362151/o_200513012151a5b1815af9ec71614f415be98c0b2f5d.jpeg");
    background-position: initial;
    background-size: cover;
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-origin: initial;
    background-clip: initial;
    height:100%;
    width:100%;
   opacity: 0.80;
    }