After you installed the lastest release of Joomla! 1.5.x, one thing you might think about customizing is the copyright message that displayed at the bottom of your newly created Web site. While it's nice to give credit to the good people of Joomla! Project, you probably want to show there a copyright message for the contents you produce.
Since the module footer is actually responsible for displaying that copyright message, it is a easy task to change the message by modifying the language file for that module.
Firstly according to the language(s) you are using for your site, open the language file for module footer in your editor. For instance, you should open the file language/en-GB/en-GB.mod_footer.ini for English or language/zh-TW/zh-TW.mod_footer.ini for Traditional Chinese.
Find the following lines in the file you just opened.
FOOTER_LINE1=Copyright © %date% %sitename%. All Rights Reserved. FOOTER_LINE2=Joomla! is Free Software released under the GNU/GPL License.
Change those linse to messages you like to show at the footer. Note that %date% in the FOOTER_LINE1 means the current year and %sitename% is the site name you set as part of the global configuration for your Joomla! Web site.
Now save the file and refresh your Web site. You should see the updated messages shown at the footer.
While this works for many cases, you must be aware that some templates directly put footer messages in the template file. In that case, you can either change the footer in the template or modify the template to include a area for footer module.