1. 轮廓

1. 背景：background

background-color
background-image
background-repeat
background-attachment
background-position
简写：
　　background: #ffffff url("tree.png") no-repeat right top;

2. 边框：border

border-style 必须
border-color
border-width
border-radius 属性用于向元素添加圆角边框

简写：固定顺序
　　border: 5px solid red;

3. 外边距：margin

margin: 25px 50px 75px 100px;