umask bafflement

So, here’s some text from the FAQ of my webhost:

As a security precaution, CGI and PHP scripts run with different user credentials than you do when you edit your files. Although the CGI/PHP user has significantly less privileges overall, it is possible to create a situation where an application creates files or directories that you do not have permission to access or remove via FTP or ssh. This typically happens if an application’s umask is set incorrectly; the resulting files or directories will be owned by the “web” user and will not be group or world writable. (Correct umasks are 0 or 002, depending on the expected group ownership. A umask of 0 should work for most web applications, and does not compromise security on our system the way it does on some shared hosts.)

I’m on Comicpress, a Mac OS X 10.5.8, using Cyberduck for my FTP stuff. I’ve also discovered permissions-changing with chmod stuff in Terminal, though I have no idea how I did it, I just followed this handy tutorial. My comics thumbnails aren’t uploading and they’re not editable. My host has given me permissions back on the appropriate folders, and according to these FAQ guidelines, I need to change the umask stuff. I don’t know what this means or how to do it.

Soooo… can anyone help me? :/ I don’t even really know which words to google, because I don’t know what I’m looking for!

Thanks for reading this far. 🙂

Lotte