Panels can be shown or hidden in an animated style. Panel animation can be enabled or disabled by using the Properties dialog.
If the panel has hide buttons at both ends, then clicking one of the hide buttons will cause it to slide in or out of view. If the panel is set to Autohide, then the panel slides into view when you move your mouse to the edge of the screen, and slide out of view again when you move the mouse away. If panel animations are disabled, then there will be no sliding effect. Panels just abruptly appear or disappear from view.
To turn off panel animation, type the following command:
# gconftool-2 --type bool \ --set /apps/panel/global/enable_animations false