Fail to get a response from the server after it posts data to the host

Hello,

I used the POST method to post the data and the xml file to the server but in reponse I get the Error: the remote server an error (500) Internal Server error, Can anyone tell me this error message really means?. Is the connection to other server failed or the data itself has a problem.  Thanks
ASCIIEncoding encoding = new ASCIIEncoding();
postData += "?userID=" + xxx;
postData += "&password=" Go to the complete details ...