<p id="box1">box1(幅500px)</p>
<p id="box2">box2(幅500px border 1px)</p>
<p id="box3">box3(margin 5px)</p>
<p id="box4">box4(padding 5px)</p>

#box1     {
          width: 500px;
          background-color: blue;
}
#box2    {
          width: 500px;
          background-color: blue;
}
#box3    {
          width: 500px;
          background-color: blue;
          margin: 5px;
}
#box4    {
          width: 500px;
          background-color: blue;
          padding: 5px;
}