"In this tips and tricks article you will see a few little
tweaks you can make to the GNOME panel to make your desktop more
productive, efficient, and just plain cooler. NOTE: For this
article I will be using GNOME 2.28. If you are using an earlier
release some of these tips may not work.
"You may have found yourself in this situation. You create a new
panel, set it on either the left or right side of the desktop, and
configure it to auto-hide, only to find that you can not un-hide
that panel. This is a problem that can happen when certain elements
are added to a panel (the GNOME Main menu for example). It seems no
matter how long you hover your mouse near the edge of that hidden
penal (the action to un-hide the panel), it won't come out. If this
is the case, fret not, there is a way to get it back. For the GNOME
desktop there is a tool called gconf-editor. This tool allows you
to set configuration options for all tools and applications in
GNOME, without having to open up the tool or application."