X Rezise and Rotare (xrandr) is a utility available in your Linux system for reseting and resizing your screen resolution. It is a command line utility. so if your display disapperaed ?? No problem you can do it from a Terminal (Press Ctrl+Alt+f1).
First You have to find the possible resolutions with xrandr -q
$ xrandr -q
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 1024
VGA connected 1024x768+0+0 (normal left inverted right x axis y axis) 270mm x 200mm
1024x768 60.0*
800x600 85.1 75.0
640x480 85.0 85.0 75.0 59.9
720x400 70.1
Now you can set your resolution with command
$ xrandr -s 1024x768
More Details
$ man xrandr
