Script: http://www.dynamicdrive.com/dynamicindex11/submitonce.htm

Hi - I was checking out the submit once script and as stated, refreshing the page one can get around it.

what additional script could be added to prevent this?

I'd like to think of refreshing the page as a way for the legitimate user to still be able to re-submit the form in the event he/she accidently clicked on the submit button before properly filling out the form. Otherwise, you will get some frustrated users. For the record, it's possible to truly only allow one submit per browser session, by using session cookies (http://www.javascriptkit.com/javatutors/cookie.shtml).