Custom CSS Code lets you add custom CSS to the site, to different pages, from the administrator interface, without modifying the template's CSS, the template HTML or requiring any access to the server's FTP. Click here to get more information.
Click here to access the extension in the Joomla Admin interface.
Here are some examples of what you can do:
Example 1: color something in green
Example 2: add a background to a <div>
Example 3: make some text bigger
I am bigger...