Samsung SyncMaster 400DXn Owner's Manual page 170

Power Off, Screen Saver, or Power Save Mode
Turn the power off for 4 hours after 20 hours in use
Turn the power off for 2 hours after 12 hours in use
Set the Monitor to power off with the PC Display Properties Power Scheme.
Use a Screen saver if possible - Screen saver in one color or a moving image is recommended.
Change the Color Information periodically
Note
• Use Two different colors
Rotate the Color Information with 2 different colors every 30 minutes.
Avoid using a combination of characters and background color with large difference in luminance.
Avoid using Grey colors, which can cause Image retention easily.
Avoid: Colors with big difference in luminance (Black & White, Grey)
Change the characters color periodically
Use Bright colors with little difference in luminance
- Cycle : Change the characters color and background color every 30 minutes