Ubuntu notifications, those grey bubbles for incoming instant messages and such, are in the top right corner under the system tray area by default. Many applications, like Google Chrome browser, place lots of controls there and notifications might block them. Also, you might prefer some other corner due to your personal taste. The application for responsible for those bubbles is called notify-osd.
Here are instructions how get a custom notification-osd which can read a config file where you can specify settings for the notifications. Though it requires you to install a custom notify-osd version, the instructions are plain and simple. For less hardcode users, there also exists a version with graphical user interface to configure notify-osd.