Code:
<html>

<head>




<script language=Javascript type="text/javascript">

function checkname(x)
{

if(x==""){
window.alert("you must enter a username")


reg.username.select()
reg.username.focus()


}

}


function checkpass(y)
{

if(y==""){
window.alert("you must enter a password")
reg.password.select()
reg.password.focus()

}


}
</script>

</head>
<body>


<form  name=reg method="POST" action="login.php">
	<p>&nbsp;</p>
	<p><b><font size="5">
	 You must login first before you order any book</font></b></p>
	<p>
	Username
	<input type="text" name="username" size="20" 
		onblur="checkname(document.reg.username.value);"></p>
	
	<p>Password
	<input type="text" name="password" size="20" 
		onblur="checkpass(document.reg.password.value);"></p>
	
</form>

</body>

</html>

there is a bugs(script error) in this script,can anyone able to modify it to a bugs free code?
The warning will pop up non-stop!
U may try to run it for better understand my problem.Thanks.