Font size in mozilla

Dear all,

I would like to have a "larger written"
version of mozilla. What I did :
went to "Preferences",
tried to increase the size of some fonts,
(it works for some mail) but not for
the menubar for instance,
tried to change the "display resolution".

And there I don't understand a thing.
Sometimes it gives me what I want but when
I restart, this customisation is lost, sometimes
it becomes all small ?????

Any pointer would be welcome!
Best,
Amities,
Olivier

(mozilla 1.4, suse 8.1)

Olivier Ramare