Your iframe works well with Firefox, Safari and Chrome, but it doesn't work in IE. I have managed to find out the reason: The site I'm trying to access has some jquery as it needs pagination. The pagination links work in all othe rbrowsers, but not IE. I have also managed to find a solution, but unfortunatelly, as I don't 'speak' ajax, I have no idea where to start fixing your code... You can check the issue on my site at: Spicer Travel
The resolution is: here
Please note that the question on that page is not my issue, but the answer No 7 seems like is the correct one (well, it makes most sense...)
Is there something I can insert in the admin input fields for your plugin or you need to fix the plugin itself?