CSS 使用伪元素的仅底部阴影
示例
JSFiddle：https://jsfiddle.net/UnsungHero97/80qod7aL/2/
的HTML
<div class="box_shadow"></div>
的CSS
.box_shadow {
background-color: #1C90F3;
width: 200px;
height: 100px;
margin: 50px;
}
.box_shadow:after {
content: "";
width: 190px;
height: 1px;
margin-top: 98px;
margin-left: 5px;
display: block;
position: absolute;
z-index: -1;
-webkit-box-shadow: 0px 0px 8px 2px #444444;
-moz-box-shadow: 0px 0px 8px 2px #444444;
box-shadow: 0px 0px 8px 2px #444444;
}