Let's say a web server administrator has configured his web server to deny traffic from my IP address or address range and throws an http 403 forbidden when I hit the site. (In this scenario I am trying to access the server over the Internet and he knows the external address of the network my traffic originates from.)
Is there a way to prove that he is blocking my IP address/range aside from exhaustively showing (which is impossible) that I can successfully access the site from other IP ranges? Assume I am unable to communicate with the maintainer of the system.