function handleMenuRequest(req) {
    writeThis(req.responseText, "leftnav");
}

ajaxSucceededToLoad = sendRequest("menu.html", handleMenuRequest);
if (!ajaxSucceededToLoad) { // IE prohibits loading local files
    writeThis("<iframe src=\"menu.html\" width=210 height=600 marginheight=0 marginwidth=0 frameborder=0 scrolling=\"no\"></iframe>", "leftnav");
}