Problem: You try to delete files in the file manager in your control panel, but you cannot remove them, and your account is over quota.
Solution: Use your FTP account to login and remove the files that you no longer need to clear up your disk space.
Reason: The control panel sees that your account is over quota. The control panel file manager creates temporary files under your account so that it can perform certain actions like file deletion. However, since the account is over quota, the control panel will no longer allow new files to be created or written to. Because of that the operation will fail with an error. using your FTP account does not create files it simply issues the delete command to the server and the files will be removed.