How do I do this one?

Ok i am making a simple registration script that would ask for First and Last name and city and etc but I also want a confirm page which I already did. But my question is this...

Lets say the user filled out his first and last name but made a typo on his city, well if he hits a back link which I added all of the form fields are now empty, how can i make it if he does go back all the fields are still filled in??

Either put the form values into a hidden form on the confirm page and have the back link submit them back to the main form page, or store the values in a session variable and read them out of the session on the main form page.

Give them a link to go "back" and edit the details. Then they won't need to use their back buttons.