<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<script src="js/jquery-1.8.3.min.js"></script>
<style>
*{padding: 0; margin: 0}
.box{
position: fixed;
width: 100%;
height: 100%;
background: rgba(0,0,0,0.2);
display: none;
}
.box1{
width: <a href="https://www.baidu.com/s?wd=500px&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1dBPWbsuy7Bn1-WmvmYnWbY0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1Rznjf4n1mvnWn3njDYnjfsPf" target="_blank" class="baidu-highlight">500px</a>;
height: <a href="https://www.baidu.com/s?wd=500px&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1dBPWbsuy7Bn1-WmvmYnWbY0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1Rznjf4n1mvnWn3njDYnjfsPf" target="_blank" class="baidu-highlight">500px</a>;
position: fixed;left: 50%; top: 25%;
<a href="https://www.baidu.com/s?wd=margin-left&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1dBPWbsuy7Bn1-WmvmYnWbY0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1Rznjf4n1mvnWn3njDYnjfsPf" target="_blank" class="baidu-highlight">margin-left</a>: -250px;
border: 1px solid #000000;
}
</style>
<script>
</script>
</head>
<body>
<div class="box">
<div class="box1">
<a href="javascript:;" onclick="jQuery('.box').hide()" class="close">关闭</a>
</div>
</div>
<a href="javascript:;" onclick="jQuery('.box').show()" class="show">显示</a>
</body>
</html>
完全可以去掉href,这里只是个示例,完全可以用button代替,看自己的习惯,我这里用的是a标签
如何没有居中的话 可以吧fixed换成auto尝试一下