"The requested URL was not found on this server"

<?php 
// Connect to the MySQL database  
    include "storescripts/connect_to_mysql.php";
// Check to see the URL variable is set and that it exists in the database
if (isset($_GET['id'])) {
	// Use this var to check to see if this ID exists, if yes then get the product 
	// details, if no then exit this script and give message why
	$sql = mysql_query("SELECT * FROM products WHERE id='$id' LIMIT 1");
	$productCount = mysql_num_rows($sql); // count the output amount
    if ($productCount > 0) {
		// get all the product details
		while($row = mysql_fetch_array($sql)){ 
			 $product_name = $row["product_name"];
			 $price = $row["price"];
			 $details = $row["details"];
			 $category = $row["category"];
			 $subcategory = $row["subcategory"];
			 $date_added = strftime("%b %d, %Y", strtotime($row["date_added"]));
         }
		 
	} else {
		echo "That item does not exist.";
	    exit();
	}
		
} else {
	echo "Data to render this page is missing.";
	exit();
}
mysql_close();
?>