To edit footer’s in Magento follow these steps:
For the frontend:
app\design\frontend\default\default\template\page\html\footer.phtml
or
app\design\frontend\your-interface\your-theme\template\page\html\footer.phtml
For the backend:
(If you want to edit footer in back end):
app\design\adminhtml\default\default\template\page\footer.phtm
or
app\design\adminhtml\your-interface\your-theme\template\page\footer.phtm
