border-bottom 简写属性把下边框的所有属性：border-bottom-color，border-bottom-style 与 border-bottom-width设置到了一个声明中。这些属性描述了元素的下边框样式。
border-bottom: 1px; border-bottom: 2px dotted; border-bottom: medium dashed blue;
与所有的简记属性相同， border-bottom 定义了它所有可以定义的属性，即使他们并没有被显式地定义。它把所有未被显式定义的参数都设置为了默认值，这意味着这些值将被定义为：
border-bottom-style: dotted; border-bottom: thick green;
它和以下的代码是等价的：
border-bottom-style: dotted; border-bottom: none thick green;
顺便一提，在 border-bottom 之前定义的border-bottom-style的值因此被忽略了.
由于border-bottom-style并没有默认值, 未被定义的 border-style 参数的值将被设置为无，也就是无底边框.
|
初始值 |
as each of the properties of the shorthand: border-bottom-width: medium border-bottom-style: none border-bottom-color: currentcolor |
|---|---|
|
适用元素 |
all elements. It also applies to ::first-letter. |
|
是否是继承属性 |
no |
|
适用媒体 |
visual |
|
计算值 |
as each of the properties of the shorthand: border-bottom-width: the absolute length or 0 if border-bottom-style is none or hidden border-bottom-style: as specified border-bottom-color: computed color |
|
Animation type |
as each of the properties of the shorthand: border-bottom-color: a color border-bottom-style: discrete border-bottom-width: a length |
|
正规顺序 |
order of appearance in the formal grammar of the values |
-
border-bottom-width：medium
-
border-bottom-style：none
-
border-bottom-color：currentcolor
Applies to all elements. It also applies to [`::first-letter`](::first-letter). [Inherited](inheritance) no Media visual [Computed value](computed_value) as each of the properties of the shorthand:
-
border-bottom-width：绝对长度或0如果border-bottom-style是none或hidden
-
border-bottom-style：具体规定
-
border-bottom-color：计算颜色
Animation type as each of the properties of the shorthand:
-
border-bottom-color：颜色
-
border-bottom-style：离散
-
border-bottom-width：长度
Canonical order order of appearance in the formal grammar of the values
语法
速记属性的三个值可以按任意顺序指定，其中一个或两个可以省略。
值
<br-width> 见border-bottom-width.<br-style> 见border-bottom-style.<color> 见border-bottom-color.
正式语法
<br-width> || <br-style> || <color>where <br-width> = <length> | thin | medium | thick <br-style> = none | hidden | dotted | dashed | solid | double | groove | ridge | inset | outset <color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color> where <rgb()> = rgb( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] ) <rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] ) <hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] ) <hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] ) where <alpha-value> = <number> | <percentage> <hue> = <number> | <angle>
示例
<div> This box has a border on the bottom side. </div>
div { border-bottom: 4px dashed blue; background-color: gold; height: 100px; width: 100px; font-weight: bold; text-align: center; }
规范
|
Specification |
Status |
Comment |
|---|---|---|
|
CSS Backgrounds and Borders Module Level 3The definition of 'border-bottom' in that specification. |
Candidate Recommendation |
No direct changes, though the modification of values for the border-bottom-color do apply to it. |
|
CSS Level 2 (Revision 1)The definition of 'border-bottom' in that specification. |
Recommendation |
No significant changes. |
|
CSS Level 1The definition of 'border-bottom' in that specification. |
Recommendation |
Initial definition. |
浏览器兼容性
|
Feature |
Chrome |
Edge |
Firefox (Gecko) |
Internet Explorer |
Opera |
Safari (WebKit) |
|---|---|---|---|---|---|---|
|
Basic support |
1.0 |
(Yes) |
1.0 (1.7 or earlier) |
4 |
3.5 |
1.0 (85) |
|
Feature |
Android |
Edge |
Firefox Mobile (Gecko) |
IE Phone |
Opera Mobile |
Safari Mobile |
|---|---|---|---|---|---|---|
|
Basic support |
1.0 |
(Yes) |
1.0 (1.0) |
(Yes) |
(Yes) |
(Yes) |
