Mozilla has a Master Password feature that will remember
login/passwords for websites, news servers, etc. and unlock
them all with one PW. It may not be set up by default, look
in Edit->preferences->privacy & security->master passwords.
If this is working you should have to enter your l/p the
first time you use the server, and check the box to have it
remember. Thereafter all you need to enter is the master
password.
That's the way it /should/ work, unfortunately there are
some bugs that you may encounter. If the server thinks
you've been idle too long and needs the l/p again, Moz will
pop up a request for both the login and password (not just
the master password, as it should) and the message you
clicked on will be irretrievable. This can be very
frustrating, if the server's l/p are difficult to remember
and if you really wanted to see that message.