body {
    font-size: 15px;
    padding: 0;
    margin: 0;
    font-family: "微软雅黑","宋体",Arial;
    width: 100%;
    height: 100%;
    background: #205424 url(https://www.cnblogs.com/images/cnblogs_com/JerryZao/1352316/o_719fa9c3t9f97feeb311e_690.jpg) no-repeat top 
    center fixed;
    background-size: cover;
  }