Permission Denied is an error that occurs when you upload files or your users upload files and the user_web directory has not the right user permissions (or user rights). Make sure that the user-files directory (e.g. user_web) has the chmod 777 rights. You can set and view them with your ftp client or when logging in via shell.
If you have many user files the fastest way is to login via shell and the to insert:
chmod -R 777 user_web