1.   Make sure that you have your permissions set on the
  files mailman.cgi and cgi-lib.pl, so that both are
  executable.  The exact mechanism of doing this is different
  on every operating system.  On unix, make sure that the
  permissions on both files read "-rwxr-xr-x" when you do an
  "ls -alt".  You manage this with "chmod 755 mailman.cgi cgi-
  lib.pl".  If you're using any    other OS, ask an expert on
  your OS.
2.   Make sure that your web server understands that a file
  ending in ".cgi" (or “.pl” or whatever your copy is called)
  is a CGI script and that it should run "mailman.cgi" when
  you invoke it.  If your web server isn't happy with the
  ".cgi" extension, feel free to rename it to ".pl" or
  ".runthis" or whatever makes your web server happy.  If you
  change the extension, or even the name, of mailman, you
  shouldn't have to change anything else and it should just
  run.  MailMan dynamically identifies its own location each
  time it runs.  This one varies from web server to web
  server, and if you don't know how to deal with this issue,
  ask an expert on your web server.
3.   Make sure that MailMan's templates are readable to your
  web server.  Keep in mind that just because they are marked
  readable to you, they are not necessarily marked readable to
  your web server, since the server generally runs as a
  different user.  In Unix, you probably want your permissions
  for your "t_*.htm" files to read "-rw-r--r--", which you can
  achieve with "chmod 644 t_*.htm".  On any other OS, if you
  don't already know how to do it then ask an expert on your
  OS.
4.   Make sure that MailMan's templates are located in the
  directory that your web server will set to the 'current'
  directory when MailMan runs.  This will USUALLY be the same
  directory that the script is located in, but not
  necessarily.  Some web servers set the current directory to
  places other than where the script itself is located.  If
  you have one of these servers and MailMan runs but your
  templates are AWOL, consult with your sysadmin or an expert
  on your web server, or see section 5.7 of this FAQ.