Restore Ubuntu Panels Back To Their Default Settings

As an Ubuntu user, there comes a time (or there will come a time) when you are playing around with Ubuntu/Gnome, trying different themes, different engines, different window managers, etc, and all of a sudden you run into a problem where the Panels go awry. However there is a fix for this: 

Open the Terminal. 
Once the Terminal window opens, enter the following command at the prompt:

gconftool - -recursive-unset /apps/panel 

(Remember: There should be no spaces between the two dashes before shutdown.)

Then enter the next command:

rm -rf ~/.gconf/apps/panel

And enter one more command:

pkill gnome-panel

Both top and bottom panels will appear (if missing) with their default settings.
Hope this helps.