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Cross domain iframe issue
If you have access to the iframed page you could use something like easyXDM to make function calls in the iframe and return the data.
If you don't have access to the iframed page you will have to use a server side solution. In PHP you could do something quick and dirty like:
<?php echo file_get_contents('htp://url_of_the_iframe/content.php'); ?>
There is a simple way.
You create an iframe which have for source something like "http://your-domain.com/index.php?url=http://the-site-you-want-to-get.com/unicorn
Then, you just get this url with $_GET and display the contents with file_get_contents($_GET['url']);
You will obtain an iframe which has a domain same than yours, then you will be able to use the $("iframe").contents().find("body") to manipulate the content.
If you have an access to that domain/iframe that is loaded, then you can use window.postMessage to communicate between iframe and the main window.
There's a workaround to achieve it.
First, bind your iframe to a target page with relative url. The browsers will treat the site in iframe the same domain with your website.
In your web server, using a rewrite module to redirect request from the relative url to absolute url. If you use IIS, I recommend you check on IIRF module.