I've asked one question about this a month ago, it's here: http://stackoverflow.com/questions/3362399/post-method-to-communicate-directly-with-a-server.
And I still didn't get the reason why sometimes I get 404 error and sometimes everything works fine, I mean I've tried those codes with several different wordpress blogs. Using firefox or IE, you can post the comment without any problem whatever wordpress blog it is, but using python and "post" method directly communicating with a server I got 404 with several blogs. And I've tried to spoof the headers, adding cookies in the code, but the result remains the same. It's bugging me for quite a while... Anybody knows the reason? Or what code should I add to make the program works just like a browser such as firefox or IE etc ? Hopefully you guys would help me out!