Here's a problem that plagued me a few years ago, and I'm pretty sure
the situation hasn't improved since then, at least not in IE. Maybe
HTML5 should say something about it.
Use case: have the UA offer a "save as" dialogue, including the filename.
Mechanism: Content-Disposition HTTP header, as defined in RFC2616
Content-Disposition: attachment; filename=fname.ext
Problem: this works fine in all browsers, as long as the filename does
not contain non-Latin1 characters.
RFC 2231 (<http://greenbytes.de/tech/webdav/rfc2231.html>) defines an
escaping, and that is supported by Firefox. Example:
Content-Disposition: attachment; filename*=utf8''D%C3%BCrst.ext
IE does not support RFC 2231 (as of IE7), but allows percent escaped
UTF-8, such as in:
Content-Disposition: attachment; filename=D%C3%BCrst.ext
However, that only works when IE is configured for UTF-8 URL encoding,
which is (as far as I recall) not the default in countries using Asian
Proposal: require UAs to support RFC 2231 (UTF-8 variant).