Quick update. I do find that Chrome's inspector to be much more intuitive than Firefox's tools for inspecting the elements. Firefox's Web Developer tools provide more information on the underlying CSS styles - to some extent. It appears that Firefox's "View Style Information" tool for inspecting the CSS interprets the style information as noted above. The actual container.css has no reference to the "-ltr-source" type elements. My guess is that it has something to do with the "-moz-border-...." style elements within the .containermaster_blue class in the container.css file.
In any event, Firefox shows the classes and styles from the DesktopModules\Events\Themes\Default\default.css file. I also noticed another "Themes" directory. A google of this led me to the DNN site -
http://www.dotnetnuke.com/Community...fault.aspx This has a brief explanation on how to modify an Events module "theme". In a nutshell, it states to copy an existing theme (i.e. the default.css file in that directory) and modify to your requirements.
Follow up will include whether to implement this as a skin/container or direct file manipulation.