Comment 251 for bug 25830

I suggested a more general solution in bug 185618 comment 61 (about adding an option to render content in Firefox whenever "Save As" comes up immediately).

I suggest using an error/info page for content of a type for which there is no handler or for content for which the handler fails, so anytime Save As comes up there is some content behind it. In the case of an unknown type, the error/info page would appear as a placeholder, which would prevent unknown types from cutting off user activity, and make room for a separate "Reinterpret Content" sheet with which the user could override the provided content-type to one which Firefox can render.