Form not working in Firefox

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Hello everyone. On our non-profit website, we have a Postpartum Depression test women can take and see their score. The problem with the form is that it isn't working in firefox - it is only working in IE & Safari. When someone completes the test, the correct thing that happens is an alert box comes up with their score and one of 3 messages.

http://www.healthystartpittsburgh.org/index.php/resources/edinburgh...

Changing the button to 'submit' has not worked - it only refreshes the page. We have also tried 'return false' and other methods...I'm sure it's something small in the code? THANK YOU! Help would GREATLY BE APPRECIATED!