From Fedora:

  https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=164781

Basically, its a non-expanded panel, snapped to the bottom-right of the screen
which contains some launchers and a pager applet.

When you log out and back in again, the panel moves to the left away from the
edge of the screen.

Problem here is that when the pager applet starts up first it momentarily takes
up a lot more space (width-wise) than it should and so expands the panel,
causing the panel's position to change. When the pager applet goes back to its
normal size, the panel stays in that new position.

Two solutions:

  1) Make the pager take up a minimal width until it gets its proper size
     allocation. Right now, it initially assumes each workspace will be
     48x48. Probably better to assume 1x1 instead.

     Of course, that only works where you know that the pager is going to
     have to operation on a height constrained basis and that the parent
     was going to allocate the maximum available height. If the pager widget
     was going to be in a normal app, assuming 1x1 would suck because that's
     all we'd ever be allocated.

     Probably best to have a wnck_pager_set_workspace_size() API or something.

  2) Make the PanelToplevel persist any position changes which aren't explicitly
     requested by the user. So, unless you drag the panel to a new location,
     it will always try to go back to its original position, even if applets
     change size and stuff.

     This is the way PanelWidget currently works with applet positions - the 
     "constrained position" is the applet's position as constrained by size
     changes, whereas "pos" is the position that the user last moved it to.