FTP and Imbris directories have "permissions" assigned that
control who can "read" (view and download) and "write" (modify and upload)
files, and who can create, delete, and rename directories and files. You
will get the Permission Denied error message if you try to perform
an action for which you do not have the proper permissions.
For example, when you visit a public FTP site using anonymous
FTP, you will have permissions to move around in the pub (public) areas of
the site, as well as read and download the files that have been made
publicly available. You may even be able to upload your own files into a
special upload directory. However, you won't have the necessary
permissions to download files from non-public directories, or to delete
files on the server.