problem in showing iframe from other website

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ASP.NET

IFrame

Hi all,
we are intregating some 3rd party services in our site. For this;
in our website there is page which has a iframe we are gonna get webpage from other website in that frame.
our website implements Ticket based forms authentication.
for authorization we use url authorization ie we specify folder location in web.config file. If the issue is of URL authorization,
how to provide URL for other website page?
The problem is other website page doesn't get displayed / loaded in our website. If we do intregation in a separate project it works fine.
Following is the message what we found when did inspect element for iframe:

<iframe width="400" height="400" frameborder="0" src="xyz.aspx">
Frames are currently disabled or not supported by your browser.  Please click <A HREF="xyz.aspx">here</A> to continue ....
</iframe>

thanks in advance