I'm done some online research, including Adobe's online help manual but I can't seem to discern a clear answer. In the 'Save For Web' dialogue box, there is a parameter called 'Preview' with a drop down menu. By default it is set at 'Monitor'--the only other setting that seems relevant is the last one that is 'Use Document Profile'.
I color manage all my work. If I'm going to the web I'll convert it to sRGB before this step. I also work from a color managed workflow and profile my monitor with a colorimeter.
I don't understand what either selection means in my situation: 'Monitor' or 'Use Document Profile'.