What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Sorry I guess this question was related to your other threads question http://www.jotform.com/answers/383156?
You can put restrictions like "Loose Check" and "Strict Check" so user won't be able to submit mulitple times.
Loose Check - This checks the cookies of the form submitter.
Strict Check - This checks the IP address of the form submitter.
Here's a detailed guide of how this two features works http://www.jotform.com/help/223-How-to-set-Form-Limits-Based-on-a-Unique-Question