function handleFooterRequest(req) {
    writeThis(req.responseText, "footer");
}

ajaxSucceededToLoad = sendRequest("footer.html", handleFooterRequest);
if (!ajaxSucceededToLoad) { // IE prohibits loading local files
    writeThis("<iframe src=\"footer.html\" width=600 height=50 marginheight=0 marginwidth=0 frameborder=0 scrolling=\"no\"></iframe>", "footer");
}