If you have used Ubuntu Karmic Koala 9.10, you will realize that the position of the notification area has been changed, which is a little lower than in 9.04. It is NOT a bug. The old position is used for the notification of brightness and volume, etc.. If you have a laptop, try to turn the volume up or down, or change to brightness of the screen, you should see that. However, if you don’t want that to happen, which means, you want the old position back, you may try this instruction below:
Firstly, open up the Terminal, and and the key
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 0EF28BC1
Secondly, go to System -> Administration -> Software Sources and add the below repo
deb http://ppa.launchpad.net/gilir/updates/ubuntu karmic main
Click on Close and then Reload. Alternatively, you may sudo apt-get update in the Terminal
Finally, go to System -> Administration -> Synaptic Package Manager, find the package notify-osd and right click -> Mark for Upgrade
After clicking on Apply, you should the the notification area is back to the old position.
Thanks for huyt92 at ubuntu-vn.org for the tutorial.