Hi Robert,
Thank you so much for all of your help and input. I guess in this particular case it is not being applied at all (which like you mentioned is why it is not working). I am using the uncompiled version of the viewer. Where would I need to insert the code so that my info window popup style changes are applied? I looked in the default.css file and I see the WidgetTemplateSkin and the TitlebarButtonSkin, but I could not figure out where to input the code so that my PopUpRendererSkin is applied to the regular Pop Up Configuration for the viewer. I also looked in the index.mxml but again, did not see where to apply this. I see where it is applied for individual widgets, but since this is not a widget, I could not find where to put it.
Thanks,
Carrie