::before和::after伪元素的用法 请参考http://www.cnblogs.com/starof/p/4459991.html
效果图
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.container{
width: 1000px;
margin: 10px auto;
border: 1px solid red;
}
h3.title {
color: #F2AE11;
font-size: 1.3em;
margin-bottom: 3em;
text-align: center;
font-weight: 500;
line-height: 1.1;
}
h3.title span {
display: block; /*设置为块级元素会独占一行形成上下居中的效果*/
font-size: 3em;
color: #212121;
position: relative; /*定位横线（当横线的父元素）*/
}
h3.title span:before, h3.title span:after {
content: ''; /*CSS伪类用法*/
position: absolute; /*定位背景横线的位置*/
top: 52%;
background: #494949; /*宽和高做出来的背景横线*/
width: 9%;
height: 2px;
}
h3.title span:before{
left: 25%; /*调整背景横线的左右距离*/
}
h3.title span:after {
right: 25%;
}
</style>
</head>
<body>
<div class="container">
<h3 class="title">Welcome to <span>Snapshot</span></h3>
</div>
</body>
</html>
