function getNewContent() {

var request = getHTTPObject();
if (request) {
    request.open("GET", "example.txt", true);
    request.onreadystatechange = function() {
        if (request.readyState == 4) {
            alert("Response Received");
            var para = document.createElement("p");
            var txt = document.createTextNode(request.responseText);
            para.appendChild(txt);
            document.getElementById('new').appendChild(para);
        }
    };
    request.send(null);
} else {
    alert('Sorry, your browser doesn\'t support XMLHTTPRequest');
}
alert("Function Done");

}

addLoadEvent(getNewContent);

Firefox显示：ReferenceError: addLoadEvent is not defined，至于什么情况我不太明白，麻烦各位朋友了，谢谢