Dropdownlist-Iframe-PostBack problem

[.::wireless::.]

Hi

I have a problem related with putting an aspx page in iframe.

I have an aspx page which contains 2 dropdownlists. By choosing an item from
dropdownlist1, postback occurs and according to the selected item the
content of the dropdownlist2 is filled. Everything is ok up to this point.

When I put this aspx file into iframe, the system does not work anymore.
(When I select an item from dropdownlist1, the content of the dropdownlist2
arent filled.)

So, hope someone can help me.
Thank you !