[Gnash-dev] how to uninstall?

[abec]

Hi to all,
i'm a newbie user of linux and i have installed gnash for test it's
compatibility but i have some problem with the page www.libero.it where
i have an email account. When i go on that page i can't write anymore on
firefox(in the login boxes and in the site adress box), the only way to
write is to copy some character on other programs that aren't firefox
and paste it in firefox, after that i can write what i want until i
change program. If i copy something fromm firefox into firefox it will
only paste, but i can't write. 
Now i want to uninstall gnash and wait for a release that work better,
but i dont know how to do it.
Sorry for my bad enlgish and thank you in advance for the help.

Greatings
abec