From Fedora Project Wiki

Fedora releases since Fedora 10 do not create a /etc/X11/xorg.conf file, used to configure the X server, by default. The X configuration is automatically determined each time X is started. In most cases, this works well and there is no need to manually specify X configuration information.

If you need to make manual changes to X configuration for any reason, you will first need to create a /etc/X11/xorg.conf file.

Xorg -configure

You can create a basic xorg.conf using the X executable itself. As root run:

Xorg :1 -configure

This will create the file /root/, which you can then copy to /etc/X11/xorg.conf:

cp /root/ /etc/X11/xorg.conf

and edit according to your needs.