get the URL of an iframe’s parent page, via Nicholas Zaka's article - http://www.nczonline.net/blog/2013/04/16/getting-the-url-of-an-iframes-parent/
function getParentUrl() {
var isInIframe = (parent !== window),
parentUrl = null;
if (isInIframe) {
parentUrl = document.referrer;
}
return parentUrl;
}