Questions about backports and firefox

["Wu-Kung Sun" <sunwukung@gmail.com>]

Hi, I've never used backports but would like to try the firefox
backport.  When I do so it says it will upgrade
 mozilla-firefox-locale-zh-cn [1.0.4lang20050515-1 ->
1.5.0.1lang20060327-0bpo1]
 mozilla-firefox-locale-zh-tw [1.0.4lang20050515-1 ->
1.5.0.1lang20060327-0bpo1]
and remove
 mozilla-firefox-locale-ja [1.0+rev.0.7.7-1]
 mozilla-mplayer [2.80-2 -> 3.25-5]
What is the way to get those packages?  More generally, if you install
a backport version of a package, then anything you want that depends
on that package must also have a backports version?
--
swk