效果：
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.title{
text-align: center;
position: relative;
height: 50px;
line-height: 50px;
width: 800px;
margin: 200px auto;
}
.title:after,.title:before{
content: "";
position: absolute;
top: 50%;
background: #7a7a7a;
height: 1px;
width: 35%;
}
.title:after{
left: 0;
}
.title:before{
right: 0;
}
</style>
</head>
<body>
<div class="title">css實現文字居中兩邊橫線效果</div>
</body>
</html>