For new CentOS users, here I want to show you how to change the display resolution. To change display resolution on CentOS Linux, simply go to System | Preferences | Display. Then, simply select the display resolution from the Resolution list. Please note that these values are the resolution supported by your monitor. It should be safe to select any one of them.
In case you need to change the display resolution with custom value that does not listed there, you will need to modify the file xorg.conf.
For example you want to change your display resolution to 1900 x 1200. You can execute this command on Terminal as root.
First, make backup
Then change the display to 1900 x 1200
system-config-display –reconfig –set-resolution=1920×1200
Now you must restart X by pressing ALT+Backspace. Please note that changing the resolution manually is risky. Do it at your own risk .