xhost and DISPLAY error
 

I searched all posts regarding this issue and couldn't find any answer that completely satisfied me. My problem: being a Linux newbie, I followed a tutorial on preparing Linux (Fedora Core 5) for an Oracle database install. I started linux graphically (gnome) logging in as root and started a gterm. Then I issued a xhost +<machinename.domain_name> command, still logged in as root. Then, I su to oracle (user to be used for Oracle database installation) and issued a
DISPLAY=<machine_name.domain_name:0.0; export DISPLAY command. Since then, every time I su to oracle user, I cannot open any text file using, by example, gedit. As soon as I try, an error related to display returns. The same error happens if I'm logged as root.
I tried to command xhost -<machine_name.domain_name> but same error occurs.
I'm looking for some help on where are the configuration files so I can edit them and remove the commands that leads to mentioned errors.
Any help would be very much appreciated. Thanks

I'd suggest the following: as root,
and then, as any local user:
Now you should be able to run any X client.

It worked! Many thanks!!!