/* 定制博客背景图片，url里面是图片位置信息 */
body { 
     background-color: #efefef;
     background-image:url(https://i.loli.net/2019/01/19/5c433e04be060.jpg); 
     background-repeat: no-repeat; 
     background-attachment: fixed; 
     background-position: center 0; 
     background-size: cover; 
     filter:alpha(opacity:30); 
     opacity:0.80; //背景透明度
     padding-top:0px;
  }