Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<head>
<style>
h1 {
    counter-increment: section;
}

h1:before {
    content: "Section " counter(section) " ";
}
</style>
</head>
<body>

<h1>HTML Tutorial</h1>
<h1 id="myH1">CSS Tutorial</h1>
<h1>JavaScripts Tutorial</h1>

<p>Click the "Try it" button to change the counterIncrement of the second H1 element:</p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
    document.getElementById("myH1").style.counterIncrement = "subsection";
}
</script>

</body>
</html>