Mine

<html><head><script>function checkBox(){	if (document.form1.sn.value=="") {		alert("You must type something in the Screen Name box!");		document.form1.sn.focus();		return false;	}	return true;}</script></head><body><form id="form1" name="form1" method="post" action="maketag.php" onsubmit="return checkBox();"></body></html>