Samsung 320P - Manual (Page 69)

The best way to protect your monitor from Image retention is to set your PC or
System to operate a Screen Saver program when you are not using it.
Image retention may not occur when a LCD panel is operated under normal conditions.
Normal conditions are defined as continuously changing video patterns. When the LCD
panel is operated for a long time with a fixed pattern (-over 12 hours-), there may be
slight difference in voltage between electrodes that work the liquid crystal (LC) in a
pixel. The voltage difference between electrodes increases with time, forcing the liquid
crystal to lean. When this occurs, the previous image may be seen when the pattern is
changed.
To prevent this, the accumulated voltage difference must be decreased.
Our LCD Monitor satisfies ISO13406-2 Pixel fault Class II