Thanks again. Finally, I found the reason. The website I query works as follows: (1) when the user clicks the "Search" button, the form data are POSTed to check if the record(s) exist, and if yes (2) a GET request is put together, which returns the actual result page. I was initially fooled into believing that the content I send is 'application/x-www-form-urlencoded', which was not what the website expected. After I commented out that line in my code, it works fine. Thanks to all who responded to my post.