There are often questions in the forum describing things that are caused by wrong or not existing file permissions and problems with file owners. Here are easy to install tools that may help you.
1. Filemanager, a php script that allows you to change, modify and delete files or file permissions (don't know who is the author, I took it from the forum). You can download it here, transfer it via ftp to your server and use it.
2. Webadmin, another php script (written by Daniel Wacker) that allows you to change/modify file permissions given by the server. You can download it here or from the developer s site. Transfer the php-file via ftp to your server and use it.
Instead of using this script you can also use the wb-module webbase edit, so you can work from the wb backend.
3. WbAdmin, a php script that allows you to change, modify and delete files or file permissions (don't know who is the author, I took it from the forum). You can download it here, transfer it via ftp to your server and use it. With this script you can modify several files and directories at one time.
NOTICE: All scripts should only be used in directories, that are secured with a htaccess-file.