A ban is a formal or informal prohibition of something. Bans are formed for the prohibition of activities within a certain political territory. Some see this as a negative act (equating it to a form of censorship or discrimination) and others see it as maintaining the "status quo". Some bans in commerce are referred to as embargoes. Ban is also used as a verb similar in meaning to "to prohibit".
HTTP 403 is a standard HTTP status code communicated to clients by an HTTP server to indicate that access to the requested (valid) URL by the client is Forbidden for some reason. The server understood the request, but will not fulfill it due to client related issues. IIS defines non standard "sub-status" error codes that provide a more specific reason for responding with the 403 status code.