body { 
     background-color: #efefef;
     background-image:url(https://images.cnblogs.com/cnblogs_com/fzu-wmz/1929018/o_2102070832128.png); 
     background-repeat: no-repeat; 
     background-attachment: fixed; 
     background-position: center 0; 
     background-size: cover; 
    padding-top:0px;
    opacity: 0.7

  }