Giving a alert diolog box to a webpage

This is nothing but a diolog box which appears before showing the output.
This helps us to give a caution for readers or used as wishing the reader for example welcome as shown below.


<html>
<head>
<title>Using window .alert</title>
</head>
<body>
<h2> alert window demo</h2>
<script language="JavaScript">
alert("welcome")
</script>
</body>
</html>

Output

And if you click ok , whatever you typed will be shown. This is called
the alert diolog box.