If you have to do something important using JavaScript, then you can display a warning message to the user using <noscript> tags.
You can add a noscript block immediately after the script block as follows −
<html>
<body>
<script language="javascript" type="text/javascript">
<!--
document.write("Hello World!")
//-->
</script>
<noscript>
Sorry...JavaScript is needed to go ahead.
</noscript>
</body>
</html>
Now, if the user's browser does not support JavaScript or JavaScript is not enabled, then the message from </noscript> will be displayed on the screen.
