How to postback aspx page in iframe?

Question

I have an iframe in my main aspx page and this iframe has also a aspx page. iframe's page has some controls and main aspx page has a submit button on it. Now I want to postback iframe's page on submit button's click event using javascript. So that main page remain static and iframe's page goes for a postback
UPDATE
Thanks @Kevin Babcock and @Bala R
Suppose if I need to perform a button (which is in iframe) click event through main page

Answer 1

From javascript you can try something like

document.frames["iframeid"].document.forms[0].submit();