http://plaza25.mbn.or.jp/~snip/jlp/mozilla1.3.1-jajppack-tm0.2.1.xpi
does not exists.  It seems this file is moved to
http://plaza25.mbn.or.jp/~snip/jlp/moz1.3.1-langjajp-tm0.2.1.xpi .
I only checked the MD5 of the latter file is the same as that of the
former.

Fix: Apply the following patch to japanese/mozilla-jlp port.
In addition, mirroring the distfiles of japanese/mozilla-jlp{,-devel}
on ftp.FreeBSD.org may help if it is allowed, because these distfiles
have been replaced or renamed for several times.  See (in Japanese):
  http://home.jp.freebsd.org/cgi-bin/showmail/FreeBSD-users-jp/74894
  http://home.jp.freebsd.org/cgi-bin/showmail/ports-jp/13770
How-To-Repeat: Make sure /usr/ports/distfiles/mozilla1.3.1-jajppack-tm0.2.1.xpi
does not exist and do:
  $ cd /usr/ports/japanese/mozilla-jlp
  $ make fetch
  >> mozilla1.3.1-jajppack-tm0.2.1.xpi doesn't seem to exist in /usr/ports/distfiles/.
  >> Attempting to fetch from http://plaza25.mbn.or.jp/~snip/jlp/.
  fetch: http://plaza25.mbn.or.jp/~snip/jlp/mozilla1.3.1-jajppack-tm0.2.1.xpi: Not Found
  >> Attempting to fetch from ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/distfiles/.
  fetch: ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/distfiles/mozilla1.3.1-jajppack-tm0.2.1.xpi: File unavailable (e.g., file not found, no access)
  >> Couldn't fetch it - please try to retrieve this
  >> port manually into /usr/ports/distfiles/ and try again.
  *** Error code 1

  Stop in /usr/ports/japanese/mozilla-jlp.