border syntax:
border：<line-width> || <line-style> || <color>
<line-width> = <length> | thin | medium | thick
<line-style> = none | hidden | dotted | dashed | solid | double | groove | ridge | inset | outset
默认值：看每个独立属性
适用于：所有元素
继承性：无
动画性：看每个独立属性
计算值：看每个独立属性
相关属性：[ border-top ] || [ border-right ] || [ border-bottom ] || [ border-left ]
border value:
<line-width>： 设置或检索对象边框宽度。
<line-style>： 设置或检索对象边框样式。
<color>： 设置或检索对象边框颜色
line-style attribute
| 值 | Description |
|---|
| none | Define no borders. |
| hidden | Same as "none". Except when applied to tables, for which hidden is used to resolve border conflicts. |
| dotted | Define a dotted border. Renders as a solid line in most browsers. |
| dashed | Define dashed line. Renders as a solid line in most browsers. |
| solid | Define a solid line. |
| double | Define double line. The width of the double line is equal to the value of border-width. |
| groove | Define the 3D groove border. The effect depends on the value of border-color. |
| ridge | Define the 3D ridge border. The effect depends on the value of border-color. |
| inset | Define the 3D inset bounding box. The effect depends on the value of border-color. |
| outset | Define the 3D outset bounding box. The effect depends on the value of border-color. |
| inherit | Specifies that the border style should be inherited from the parent element. |
