//droplinemenu.buildmenu("droplinetabs1");

Element.addMethods('iframe', {
    doc: function(element) {
        element = $(element);
        if (element.contentWindow)
            return element.contentWindow.document;
        else if (element.contentDocument)
            return element.contentDocument;
        else
            return null;
    },
    $: function(element, frameElement) {
        element = $(element);
        var frameDocument = element.doc();
        if (arguments.length > 2) {
            for (var i = 1, frameElements = [], length = arguments.length; i < length; i++)
                frameElements.push(element.$(arguments[i]));
            return frameElements;
        }
        if (Object.isString(frameElement))
            frameElement = frameDocument.getElementById(frameElement);
        return frameElement || element;
    }
});	
<!-- Paste this snippet into your existing code  -->