html css实现弹出框遮罩层效果

编辑代码

<!DOCTYPE html>
<html>
<head>
<style type='text/css'>
#lightbox {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: #000;
  opacity: .6;
}
#main {
  position: relative;
  background-color: #fff;
  z-index: 1;
}
</style>
</head>
<body>
  <div id="main">Lorem ipsum, my opactiy is not affected</div>
  <p>My opactiy is affected</p>
  <div id="lightbox"></div>
</body>
</html>