If a post reqeust's body contains string "%3Cmarquee+", nginx will always return 501. Such as request: POST http://DOMAIN:PORT/test HTTP/1.1 Host: DOMAIN Content-Length: 13 a=%3Cmarquee+ response: HTTP/1.1 501 Not Implemented Server: nginx Date: Fri, 29 May 2015 04:30:49 GMT Content-Type: text/html; charset=utf-8 Content-Length: 174 Connection: close <hby hyleeonx - Other discussion