Call page after cancel in popup

Question

Hello ,

 

I have 3 pages like

 

a.html, b.html. c.html in c.html give mail coding.

I have written javascript function use prompt  box.

MY condition : 

1-when prompt box open and give email id then send mail through c.html page 

2- If not give any input value in prompt text box and click on ok/cancel button then mail send through c.html page and return main page like b.html.

ie. after click on cancel button  return to b.html page as well as send mail by c.html page?

 

Please describe how can do this?