[cd34]

It depends on how your host has permissions set on the machine. If they are running setuid or suexec, your webserver will run as your username and will be able to read/write all of the files on your site.

If they run apache in a low privilege mode, you would need the directories to be 755 to be readable, and 777 to be writeable by the webserver.

You might as your host how their servers are set up. You can also change it using FTP and see how 755 works for you. If you change it to 700 and it still works, then you are probably running on a server with suexec/setuid.