xorg.conf

Section "ServerLayout"
    Identifier    "layout1"
    Screen      0 "screen1" 0 0
EndSection

Section "Monitor"
    Identifier  "monitor1"
    Option      "VendorName" "ACME"
    Option      "ModelName" "Generic Autodetecting Monitor"
EndSection

Section "Device"
    Identifier  "videocard1"
    Driver      "nv" # change your driver here.
EndSection

Section "Screen"
    Identifier "screen1"
    Device     "videocard1"
    Monitor    "monitor1"
    DefaultDepth     24
    SubSection "Display"
        Viewport   0 0
        Depth      24
            Modes      "1920x1080" "1280x720" "1024x768"
    EndSubSection
EndSection