iframe + get response

Hi I have a "iframe" with src to other application and i don´t know how to get the response of this new page.  <p align="center"> <iframe id="iframe" runat="server" src="https://www.example.com/form.aspx" width="100%" height="500px" valign="center" frameborder="0"></iframe> </p> The response come back in the body of " https://www.example.com/form.aspx " .    Thanks for your help, I hope you understand.  
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