When using POST method to request via Nginx 0.6.33 without any post body data, you may get this error: 411 Length Required. Download nginx-0.6.33-length_required patch Save the attachment and run this command in the root path of nginx 0.6.33 source code: patch ./src/http/ngx_http_request.c<nginx-0_6_33-length_required.patch Then "make && make install && sudo /sbin/service nginx restart" and enjoy your AJAX function.