/* 定制博客背景图片，url里面是你的图片位置信息 */
body { 
     background-color: #efefef;
     background-image:url(https://images.cnblogs.com/cnblogs_com/shwee/1218109/o_bg_shw.jpg); 
     background-repeat: no-repeat; 
     background-attachment: fixed; 
     background-position: center 0; 
     background-size: cover; 
    padding-top:0px;
  }