<html>
<head>
<style>
#myDIV
{
position:absolute;
width:300px;
height:150px;
background-color:lightblue;
border:1px solid black;
}
#DIV2
{
position:relative;
top:130px;
left:30px;
width:300px;
height:150px;
background-color:coral;
border:1px solid black;
}
</style>
</head>
<body>
<p>点击“尝试一下”按钮，透过蓝色的 DIV 元素看到底下的珊瑚色的 DIV 元素。</p>
<button onclick="myFunction()">尝试一下</button>
<div id="DIV2">
<h1>Voila!</h1>
</div>
<div id="myDIV">
</div>
<script>
function myFunction()
{
document.getElementById("myDIV").style.opacity = "0.5";
}
</script>
</body>
</html>