Some time we need to some design changes on order success page in Magento and we face problem when we try to customize the design of order success page. Because, success page appear when we place an order. Once we refresh the page success page gone away. To see success page again we need to place an order again. Its is a big hassle for developer.
To view order success page just comment out few lines of code in successAction.(/app/code/core/Mage/Checkout/controllers/OnepageController.php).
Search public function successAction()