CSS-底部边框 | border-bottom

border-bottom: 1px;
border-bottom: 2px dotted;
border-bottom: medium dashed blue;

border-bottom-style: dotted;
border-bottom: thick green;

border-bottom-style: dotted;
border-bottom: none thick green;

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:

Animation type as each of the properties of the shorthand:

Canonical order order of appearance in the formal grammar of the values  

<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>

<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;
}