<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box{
width: 300px;
/* border: 1px solid red; */
}
.line{
margin: 20px 0;
line-height: 1px;
border-left: 50px solid #ddd;
border-right: 150px solid #ddd;
text-align: center;
}
</style>
</head>
<body>
<div class="box">
<div class="line">
this is line
</div>
</div>
</body>
</html>