[eluser]Nick_MyShuitings[/eluser]
Why are you forcing the user to press the back button. I read that as saying you literally show them a screen that says "you had errors. go back". Please correct me if I misunderstood.
The way to fix this is to take the POST information that you obviously had in order to validate/check for errors, and use that information to repopulate the form WITH the error message... no need for a back button whatsoever. If you are using the form validation library then the re-population is even easier to perform.
I second TheFuzzyOne in asking for at the least a url to your form.
I'd also suggest taking the time to do front-end validation if you're not already, keep them from submitting until you have assured the least amount of errors possible.