Success and error page

Hi,

I have created these two new pages (1. success page and 2. Error page) and set in settings payment section. But when I am returning after doing payment or cancelling payment, i am redirected to page that does not exist. In URL, after domain name some number start coming with error message like paged does not exist.
I think I need to put some short code in created pages (1. success page and 2. Error page). Please suggest.

Thanks,
Prashant