well, you really don't have to worry about monitor sizes, worry about the resolutions, because if you're developing your program in an 800x600 enviorment and you have a 14" monitor, it'll be the same SCALE if on a 19" monitor, if the resolution is 800X600.

Here's a little pusedo formula for you to understand this difference

lower resolution on a bigger monitor, means Picture will look bigger...

Same resolution on a smaller monitor, means picture and windows will be smaller...