效果图如下：
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="http://cdn.static.runoob.com/libs/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="http://cdn.static.runoob.com/libs/jquery/2.1.1/jquery.min.js"></script>
<style>
td{padding:10px}
.mask{position:fixed;left:0px;right:0px;top:0px;bottom:0px;background-color:rgba(0,0,0,0.7)}
.content_block{position:absolute;top:50%;left:50%;width:80%;transform: translate(-50%, -50%);background-color:#fff;border-radius:10px;}
</style>
</head>
<body >
<div class="mask">
<div class="content_block">
<table style="width:100%">
<tr><td colspan="2" style="border-bottom:1px solid #D8D8D8">提示</td></tr>
<tr><td colspan="2" style="border-bottom:1px solid #D8D8D8">内容</td></tr>
<tr style="text-align: center"><td style="border-right:1px solid #D8D8D8">取消</td><td>确定</td></tr>
</table>
</div>
</div>
<script>
</script>
</body>
</html>