<!DOCTYPE html>
<html>
<body>
<h1 id="myH1">How to change the style of a header</h1>
<p>Click the button to change the style of the H1 element.</p>
<button onclick="myFunction()">Try it</button>
<script>
function myFunction() {
document.getElementById("myH1").style.color = "red";
}
</script>
</body>
</html>