css設置圖片body全鋪滿，整個背景都是一張圖片的寫法

    body {
      background-image: url('images/1.png');
      background-repeat: no-repeat;
      background-position: center;
      background-attachment: fixed;
      background-size: cover;
      -webkit-background-size: cover;
      -moz-background-size: cover;
      -o-background-size: cover;
    }