305 Use Proxy Was defined in a previous version of the HTTP specification to indicate that a requested response must be accessed by a proxy. It has been deprecated due to security concerns regarding in-band configuration of a proxy. The requested resource MUST be accessed through the proxy given by the Location field. The Location field gives the URI of the proxy. The recipient is expected to repeat this single request via the proxy. 305 responses MUST only be generated by origin servers. Note: RFC 2068 was not clear that 305 was intended to redirect a single request, and to be generated by origin servers only. Not observing these limitations has significant security consequences. Wikipedia Many HTTP clients (such as Mozilla and Internet Explorer) do not correctly handle responses with this status code, primarily for security reasons.