Problem with window.prompt

Hi..
can anybody show me whats wrong with this script??

<html> 
<head>
<script type="text/javascript">
 
var product1=0; 
var product2=0; 
var product3=0; 
var product4=0; 
var product5=0;
var inputString;
 
var productId=1;
 
while(productId != 0) {
inputString=window.prompt("Enter Product number (1-5) (0 to stop):","0");
 
productId=parseInt(inputString);
 
if (productId >= 1 && productId <=5) {
inputString=window.prompt("Enter quantity sold: ","0");
 
var quantity=parseInt(inputString);
 
switch(productId){
case 1;
product1 += quantity*2.98;
break;
 
case 2;
product2 += quantity*4.50;
break;
 
case 3;
product3 += quantity*9.98;
break;
 
case 4;
product4 += quantity*4.49;
break;
 
case 5;
product5 += quantity*6.87;
break;
}
}
 
else if (productId !=0) {
window.alert(
"Product number must be between 1 and 5 or" + "0 to stop");
}
}
 
document.writeln("<h2>Product Totals</h2>");
document.writeln("<table border='1' width= '100%'>");
document.writeln("<tr><td width='100'><strong>Product #</strong>"+"</td>");
document.writeln("<td width='100'><strong>Total Sales</strong>"+"<td></tr>");
document.writeln("<tr><td>Product 1</td><td>"+product1+"</td>"+"
<tr><td>Product 2</td><td>"+product2+"</td>"+"
<tr><td>Product 3</td><td>"+product3+"</td>"+"
<tr><td>Product 4</td><td>"+product4+"</td>"+"
<tr><td>Product 5</td><td>"+product5+"</td>
</tr></table>");
 
//-->
</script>
</head><body>
 
</body>
 
</html>

What is it supposed to do, and what does it actually do?

It calculates total price based on the quantity entered by the user.

So what's the issue?

when I open it in IE or Firefox, only blank page appears. No window prompt for user input.

All the code is in the document head, when it should be in the body. Or, even better, define it in functions in the head, which you then call from the body. I'm not sure it's possible to call document.writeln after the document has been laid out, though; probably not.

In fact, why are you writing the document in writeln's to being with?