Help me if I'm missing something here: Aren't web parts supposed to
resize (especially horizontally) to fit if the browser is reduced in
size or the monitor resolution size is smaller?

On our site, the pages look fine on the workstations they were
developed, but everyone has to scroll horizontally on other screens.

In my experiments, the web parts and zones seem to resize down a bit
and then stop. Looking at the settings, everything is set to "adjust
to fit zone" and nothing is set to a specific pixel size.

What else am I missing?