body {
    opacity: 0.8;
    filter: alpha(opacity=75);
   // background: #C2ECFF url(https://images.cnblogs.com/cnblogs_com/TnT2333333/901421/o_57592508_p0.jpg) no-repeat top center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}