Use a virtual screen larger than the physical screen size.
Often this can be done by:
- Adding something like "Virtual 1024x800" to
- Restarting X11 (using Ctrl+Alt+Backspace on those distributions/configurations that support this).
What if I have Ubuntu?
On Ubuntu Ctrl+Alt+Backspace does not restart X11. If using Ubuntu, your options are one of:
sudo /etc/init.d/gdm restart
System -> Preferences -> Keyboard -> Layout -> Key to kill X -> [/] Ctrl+Alt+BS
- Reboot if you can't figure out a better way to restart X11.
Moving windows that are larger than screen
As JamesGecko's Answer suggests ...
The KDE window manager, Kwin "lets you easily move windows by pressing the ALT button. You can then just click on a window's content. While you hold the left mouse button pressed, windows will move". - KDE.org
You can therfore grab a window somewhere in it's lowest visible region and drag it up to reveal any [OK], [Cancel] or other buttons at the bottom that were formerly offscreen and inaccessible.