How to enable cross site scripting for some sites in browser- ie/firefox/opera/chrome

Hello,

I have a web application that submits data to a 3rd party site, later the application uses javascript to parse through the response from 3rd party site (which is set to a specified target IFrame)…

I want to be able to parse through the content of response page at child iframe… As far as I know this type of cross site scripting is not enabled by default…

Is there some way to enable such type of scripting to occur?.. Please bear in mind that the page in child Iframe is a 3rd party website over which I have no control…

If there is no way to enable such scripting, then should I use an older version of browser which allows such scripting? Or is there some hack to enable this?

I will be happy using any/either of IE/Firefox/Chrome/Opera for this purpose.
(That includes using older versions which support cross site scripting).

Regards,
Arvind.