|As jefro says, LCDs don't suffer from burn-in as such. But they can suffer from something called image persistance. Normally this is a temporary affliction. (See this reference: http://compreviews.about.com/od/mon...|
The simple answer, to me, would seem to be just to set a screen saver, either in the OS or in the monitor itself. Does the screen really have to be visible all the time?