To remove any icon from top or bottom bar in Ubuntu 12.04 OS you need to press Windows + Alt and then right click on the icon.
Here you will see following 2 option:
- Remove from panel
Now select remove from panel option, this will remove selected icon from top/bottom bar.
Similarly to edit properties of top/bottom bar press Windows + Alt and then right click on top/bottom bar.
Here you will see following 4 options:
- Add to Panel
- Delete This Panel
- New Panel
Depending on your requirement select any of option and finish your task.