sounds like you are accessing your server remotely?
within your xterm connection, export your DISPLAY and launch mozilla
(use xclock to test DISPLAY settings...)
I have the following in my .bash_profile that takes care of this:
DISPLAYHOST=$(who -mu | awk '{print $8}' | sed 's/(//' | sed 's/)//')
DISPLAYHOST=${DISPLAYHOST%%:0.0}
DISPLAY=$DISPLAYHOST:0.0; export DISPLAY
echo "DISPLAY has been set to $DISPLAY"
of-corse you need to have a browser installed
bash-3.00# pkginfo -i | grep mozilla
MOZ17 SUNWmozilla Mozilla Web browser
MOZ17 SUNWmozilla-devel Mozilla for Solaris(TM) - Mozilla Web browser - developer files
-bash-3.00$ which mozilla
/usr/sfw/lib/mozilla/mozilla