Before we have a look at the backend interface, let's focus for a while on an issue concerning site security—it's about your personal keys to the site.
In any CMS, it's vitally important to guard any "doors" through which hackers can grab hold of your site. In Joomla! 1.5, the door to the backend of the site wasn't closed securely due to the system habit of naming the root user (the Super Administrator) "admin" during the installation process. If you didn't change the name "admin" later on, hackers only needed to guess your password to be able to log in to your site.
Joomla! 1.6 rectifies this flaw by letting you enter an Admin Username during the installation process. In previous versions, you could only change this name after installation—and many site administrators apparently didn't bother.
You can now change the root user's name during the installation process (see Step 6, Configuration in the screenshot below). In the Main Configuration...