Heres the deal ........

I made a bet with a friend that I could write a working javaScript that asked the user for 2 numbers and then displayed the sum, differance, product and quotient of the 2 integers. Its a very easy script but the catch was I had to add quotes for readability and get it done in 3 minutes or less.

I got it done in less then 3 minutes but I still lost the bet because, for some reason it didn't work and now that I have paid my losers wages to my mate I'm trying to debug this thing and as easy of a script that it is ...... I can't see what I did wrong.

Its blowing my mind, so here is my script ........... WHATS WRONG WITH IT???

Code:
<html>
<head>

	<title>Quick JavaScript</title>

	<script type = "text/javascript">
	  
		var firstNumber,	   //first string entered by user
		      secondNumber,	 //second string entered by user
		      number1,		     //first number to use 
		      number2,		     //second number to use 
		      sum, 		        //sum of number1 and number2
		      product, 		      //product of number1 and number2
		      differance, 	     //differance of number1 and number2
                      quotient;		     //quotient of number1 and number2

		
		//read first number from user as a string
		  firstNumber = window.prompt("Enter first integer", "0");
		
		//read second number from user as a string
		  secondNumber = window.prompt("Enter second integer", "0");

		//converts numbers from strings to integers
		  number1 = parseInt(firstNumber);
		  number2 = parseInt(secondNumber);


			//performs operations
			  sum = number1 + number2;
			  product = number1 * number2;
			  differance = number1 - number2;
			  quotient = number1 / number2;


		//displays output of operations
		  document.writeln("The sum of " + number1 "and " + number2 + "is " + sum);
		  document.writeln("The product of " + number1 "and " + number2 + "is " + product);
		  document.writeln("The differance of " + number1 "and " + number2 + "is " + differance);
		  document.writeln("The quotient of " + number1 "and " + number2 + "is " + quotient);

	  
	</script>
</head>
<body>
</body>
</html>
The prompt windows doesn't even come up so it is something in that part of the script.

I know it is probably something blatantly obvious, but my eyes aren't catching it, maybe someone heres eyes will - Im dumbfounded.