mozilla ruun with other user permision

[deblinuxprog]

Hello

I used to open some mozilla window on the same X session but with
diferent user. 

Before i'am using redhat 9,0 and can do this with:
su user
nohup mozilla &
in a terminal window

Now i am now using a debian sarge with kde3 and this i use before don't
work now. I use gksu to do the same thing

nohup gksu -u user mozilla &

But some time mozilla don't run with the user permision and if i have
the good permision, i can't open mozilla with normal way in the K menu
with the (X)user permision i have the permision and the style of the
(gksu)user.

I know that my english is not good and hope to be understand.

I don't know if you know this problem, if i don't know how to use gksu
or if it is a bug.

Thank you