nano /etc/X11/xorg.conf.d

Section "Monitor"
        Identifier      "Default Screan"
        Option          "DPMS"
        Modeline        "800x600_60.00" 38.25  800 832 912 1024  600 603 607$
        Option          "PreferredMode" "800x600_60.00"
EndSection
__________________

nano /etc/X11/xorg.conf

Section "Screen"
       Identifier      "Default Screen"
       Device          "geforce256"
       Monitor         "S/M 950p"
       DefaultDepth    24
       SubSection "Display"
               Depth           16
               Modes           "800x600" "1600x1200" "1280x1024" "1024x768" "640x480"
       EndSubSection
       SubSection "Display"
               Depth           24
               Modes           "800x600" "1600x1200" "1280x1024" "1024x768" "640x480"
       EndSubSection

EndSection

__________________________

nano ~/.fluxbox/startup

#screen resolution

xrandr --newmode "800x600_60.00" 38.25  800 832 912 1024  600 603 607 624 -hsync +vsync
xrandr --addmode LVDS 800x600_60.00
xrandr --output LVDS --mode 800x600_60.00