body {
color: #000;
background: url(https://images.cnblogs.com/cnblogs_com/lucide/1848077/o_200915092257lcd.jpg
) top fixed;
background-size: cover;
background-repeat: no-repeat;
font-family: "Helvetica Neue",Helvetica,Verdana,Arial,sans-serif;
font-size: 12px;
min-height: 101%;
}
#header{
margin-top:20em;
}