If you want to customize the index.php, xml or image files associated with the Mambo templates via ftp you may run into a common problem relating to file permissions for Mambo.
To resolve the above download the JoomlaXplorer component from http://virtuemart.net/
This is a really useful free Mambo component which will enable you to manage and change the file and directory permissions on your server.

So if you wish to change the index.php file or image file and get the an error message saying "permisson denied" then you need to install the above component. Once the JoomlaXplorer component is installed you can navigate to the specific template directory and set the relevent CHMOD permissions on the directory. I would advise changing the permissions to 777. Once you have changed the permissons then you can make changes to the template and upload the files to your server using an FTP client. Please note always change the permissions back to 755