Thanks for the reply, felgall. I'm aware of designing for different screen sizes (i.e., different real estate available on different size monitors).
The issue I'm having is the actual size of the elements on the screen. So, for example, if I create a call-to-action button graphic on my 1920x1200 monitor, when I view the graphic on my 1680x1050 monitor the dimensions of the button looks too large. Or if I view a web page everything (font, graphics, browser, everything) appears larger on my smaller 1680x1050 monitor than it does when viewed on my larger 1920x1200 monitor.
It's making my design work difficult because I feel like I have to make all my graphics smaller than looks good to me so they are a good size when viewed on a monitor resolution that most people have.