<!DOCTYPE html>
<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>Click the "Try it" button to see through the blue DIV element:</p>
<button onclick="myFunction()">Try it</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>