使用xmlHttpRequest打开未定义的URL

Question

我正在提出这样的服务器请求：

    //document.write("getmessages.php?q="+employeee);
    xmlHttp.open("GET","../ajax/getmessages.php?q="+employeee,true);

    // define the method to handle server responses
    xmlHttp.onreadystatechange = handleServerResponse;
    // make the server request
    xmlHttp.send(null);

代码工作正常，但它试图制作一个弹出窗口，如果我打开它，就会出现：

The requested URL /undefined was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

我不确定导致此错误的原因