Conventional ergonomics guides suggest aligning the top of the monitor to where the operator looks at straight on. It seems doubtful that that still applies to today's 24" and 30" and larger displays. What was the reasoning behind that rule? What's the correct way to position a huge display?
Addendum: Would anyone have a link to research confirming the "2/3 up" rule?
Actually, the rule of thumb is to align your eyes (straight ahead) to about 3/4 up the height of viewable area of the screen. That is, about 1/4 of the screen is above eye-level, the rest is below and this should apply to any reasonable screen size.
Beyond that rule of thumb, the bottom of the screen should not be more than 60 degrees below the straight ahead horizontal viewing angle.
I have a couple of large displays (24" I think) at work. They were originally aligned to the top of my vision, and I actually found it to be kind of painful. I found myself looking at things on the bottom of the screen frequently, (taskbar, dock, status bar, clock, whatever), which meant my head was hanging down. I have a 20" display at home, where I don't have this problem.
I think it makes more sense to have your eyes aligned about 2/3 of the way up the display. This means you don't have to look too far up or down.
I have three 20" LCD's left to right no gaps between the bezels. I find looking left or right more than 1/2 of those outer screen gives me a pain in my neck. For instance I often move the browser to the left screen (using nvidia hotkeys I setup CTRL-1,2,or3) to read an article or documentation. If I have to stay on that page more than about 30seconds my neck starts to have pain. Maybe it's because I sit about 18" away from the main screen. But I think there is a limit to how far you can reasonable turn your head left or right for a period of time. So what I try to do is have the browser use the right 1/2 of the left monitor so I don't have so far to turn.
I'm waiting for the 30" LCD's to come down as I think a single 30" with a decent windows manager will do just as well. Hope this was helpful. Although it was not scientific, just my own experience.
The top of the monitor should be at or slightly below eye level. The center of the computer monitor should normally be located 15 to 20 degrees below horizontal eye level (Figure 6).
The entire visual area of the display screen should be located so the downward viewing angle is never greater than 60 degrees when you are in any of the four reference postures. In the reclining posture the straight forward line of sight will not be parallel with the floor, which may increase the downward viewing angle. Using very large monitors also may increase the angle.