Generally, there is a suggested resolution size that is dependent upon the video card.
For example, on my primary desktop machine (3 monitors x 24") the suggested resolution is 1920 x whatever. When I set it to anything different, the quality suffers.
Is it possible that you are really asking about the width-to-height ratio?
Because these have been changing in the last few years.
Perhaps this will help.
Google: Monitor Resolutions
Dave
