Value From my asp.net or html page to any other website ifra

Hi, everyone 

                      I have a page in asp.net or html i have a textbox on it. I want to pass my textbox value to any other website that is in iframe on my page. Other website is like (gmail.com) on registration page. When i click a button on my page the text box value also pass to the gamil text box as first name. Thanks a lot.