How do I adjust display contrast and brightness in Ubuntu?

"Use

sudo setpci -s 00:02.0 F4.B=xx

Where xx is the desired brightness in hexadecimal ranging from 00 (brightest) to FF (no brightness at all)."

"If you are using Ubuntu go to System > Preferences > Power management
there you find a brightness bar slider set it to the desired brightness level and to keep the change permanent check on the Make default check box"

@Bruno is right. I experienced the same problem when using Fedora 17. The keyboard hotkeys for brightness would not have any change on the brightness. Do a simple edit of your grub file as explained at http://joseblog.netau.net/tips-and-tricks/acer-adjust-brightness-problems.php