Preview DFP

<script>
    var positionTag = top.document.querySelector("#dfp-pulse");
    var correctSlot = false, parent = frameElement;
    if (!top.window.previewAlreadyDisplayed) {
        for (var i = 0; i < 5; i++) {
            if (parent == positionTag) {
                top.window.previewAlreadyDisplayed = correctSlot = true;
                break;
            } else {
                if (!parent.parentElement) break; 
                parent = parent.parentElement;
            }
        }
    }
    if ((top.window.previewAlreadyDisplayed && !correctSlot) || !correctSlot) {
        if (top.window.previewAlreadyDisplayed) console.error("Preview stopped: preview already displayed.");
        else  console.error("Preview stopped: incorrect slot.");
        document.currentScript.parentElement.outerHTML = "";
    }
</script>