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.
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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.
Unfortunatley we do not have such features.
You will have to download your form's source code and add some custom code to achieve your requirement. Please check the following thread where my colleague have explained this workaround in detail: http://www.jotform.com/answers/181798-Ability-to-show-the-Thank-You-Message-in-a-pop-up-version-so-that-users-can-simply-close-the-pop-up-window-and-go-back-to-site
The another option is to embed form in your web page using its LightBox code which will always open form in a new window.
Hope this helps.
Do get back to us if you have any questions.