Some guestbook scripts and other CGI tools require that a file have world writable access. In order to accomplish this, you'll need to explore the capabilities of your FTP client software. Most software has a selection of tools that allow you to change a file's mode. This may be under a chmod command or a section of commands referred to collectively as UNIX commands.

In order to make a file world writable, the mode should be set to 766. In order to make a file non-world writable, the mode should be set to 755. (It's generally easier to use the check boxes which most FTP clients use rather than typing in the numeric mode.)