function create_b7_iframe(htmlStr) {
            var frag = document.createDocumentFragment(),
                    temp = document.createElement('div');
            temp.innerHTML = htmlStr;
            while (temp.firstChild) {
                frag.appendChild(temp.firstChild);
            }
            return frag;
        }

        function receiveMessage(event) {
            if (event.data === "removetheiframe" && event.origin.indexOf("//b.big7.com") > -1) {
                var frame = document.getElementsByClassName('b7_iframe');
                frame = frame[0];
                document.body.removeChild(frame);
                window.removeEventListener("message", receiveMessage, false);
            }
        }
        window.addEventListener("message", receiveMessage, false);

        var fragment = create_b7_iframe('<iframe class="b7_iframe" src="//b.big7.com/layer_lp12.php?pv=1&wm=1&wmb=8386&wms=1&p=2" style="border:none; position:fixed; left: 0; top: 0; width: 100%; height: 100%; background:none repeat scroll 0 0 rgba(0, 0, 0, 0.6);z-index: 214748;"></iframe>');
        document.body.insertBefore(fragment, document.body.childNodes[0]);