If your browser makes a file downloading attempt instead of displaying the page, it can't handle
Content-Type: type; charset=name
in HTTP header, send a bug report to the development team.
If your browser is able to request character set (Russian KOI8-R character set is assumed in the example below), you'll have
HTTP_ACCEPT_CHARSET field. For example:
HTTP_ACCEPT_CHARSET = KOI8-R, ISO-8859-1; q=0.1