title: Sending custom HTTP response code from proxy
body: <p>I have a local web proxy that filters access to websites.
  If the browser is attempting to access a blocked url, the proxy responds with a HTTP 302 along with a HTML page that contains a custom message.
  This works fine for HTTP connections (HTTP GET). However, if the browser accesses a secured site (HTTPS using HTTP connect), a HTTP 302 response with custom message is not displayed by the browser and instead it displays a generic "This page cant be displayed" (in MSIE and equivalent in other browsers).
  Is there any HTTP error code that I can return from the proxy to display a custom message to the user in the browser page?</p>