body {
    background-image:url(https://images.cnblogs.com/cnblogs_com/Whiteying/1356054/o_cc020ef3d7ca7bcb5a1bc12bbe096b63f624a85a.jpg); 
    background-repeat:no-repeat;
    background-attachment:fixed;
    background-size:cover;
}
#home {
    opacity: 0.80;
}