<!DOCTYPE html>
<html>
<head>
<title>ARIA Example</title>
</head>
<body>
<div role="alert" aria-live="assertive" aria-atomic="true" id="live-region">
<!-- Dynamic content goes here -->
</div>
<script>
document.getElementById('live-region').innerHTML = "This is an important message.";
</script>
</body>
</html>