How to add A message box when page opens






<!-- this script got from www.technohackrzs.blogspot.com coded by: joo-->

<html>
<head>
<script language="javascript" type="text/javascript">
alert("Welcome to my site")
</script>
</head>
</html>       
<font face="Tahoma"><a target="_blank" href="http://technohackrzs.blogspot.in/search/label/Java%20Script/"><span style="font-size: 8pt; text-decoration: none">JavaScript Free Code</span></a></font>