At the moment this is all on the same site but once in production, I will have a resource site with all the different child iframe pages which will be used on 10 different conference site as this is for sponsor pages.
Hi Philippe, there is one crucial condition for opening a light box on the parent frame: both parent and child frame must live on the same domain. If not, the script will be blocked by any browser that respects cross-site scripting security.
Next, it’s important to realize that this is not possible with the standard WordPress plugin. It would either need a heavy modification or (better) a custom implementation of the light box script on the child page.
I’m afraid this is out of the scope of possibilities of Easy FancyBox…