CSS盒模型

盒模型的三个属性：margin，border，padding。设置方法如下：

1. border
(1)
border:2px  solid  red;
(2)
border-width:2px;
border-style:solid;
border-color:red;
(3)
border-bottom:1px solid red;
border-top:1px solid red;
border-right:1px solid red;
border-left:1px solid red;

2. padding/margin
(1)
padding:20px 10px 15px 30px;
(2)
padding-top:20px;
padding-right:10px;
padding-bottom:15px;
padding-left:30px;