#home{   
      filter:alpha(opacity=50);   
      -moz-opacity:0.8;   
      -khtml-opacity: 0.8;   
      opacity: 0.7;   
}
body{
background-image:url(https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1514300238&di=dd9e39e1cd6ae8ec95892503648f8201&imgtype=jpg&er=1&src=http%3A%2F%2Ftupian.enterdesk.com%2F2015%2Fmxy%2F6%2F14%2F12%2F3.jpg);
background-size:cover;
background-attachment:fixed;
}