body {
color: #000;
background: url(https://images.cnblogs.com/cnblogs_com/jz929/1516991/o_4.jpg
) fixed;
opacity: 0.8;
background-size: 100%;
background-repeat: no-repeat;
font-family: "Helvetica Neue",Helvetica,Verdana,Arial,sans-serif;
font-size: 13px;
min-height: 100%;
}