Changing resolution and refresh rate in ubuntu

You boot up your ubuntu box as usual. Suddenly you notice something wrong: your resolution has changed without you changing it. You go to system preference and try to change the display resolution, but there is no optinon for your preferred setting. Don't panic, there still hope for your ubuntu machine besides reformat :-).
This is what you can do to repair back the display problem. You have to reconfigure Xorg. But before you do anything, please backup your configuration file just in case anything bad happens.

Backup your xorg.conf file
$ sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup

This is how you can reconfigure Xorg

1. Stop your gdm (Gnome display manager), or kdm (KDE display manager) if you use kde desktop environment.
$ sudo /etc/init.d/gdm stop (or kdm for kde)
2. Reconfigure your xorg
$ dpkg-reconfigure xserver-xorg
3. Follow all the instruction. By default, choose 'yes' or 'ok' for every options
4. After finish reconfigure, start back gdm or kdm
$ sudo /etc/init.d/gdm start (or kdm for kde)

Hope this can help.