[Plugin: WP Super Cache] File permission error

In my logs I find a lot of errors like this:

(13)Permission denied: file permissions deny server access: /(user)/(domain)/wp-content/cache/supercache/(domain)/(page).html

I am guessing this means that some file or directory involved in the cache has the wrong permissions. What should the permissions be for the following files and directories?

wp-content/
wp-content/.htaccess
wp-content/cache/
wp-content/advanced-cache.php
wp-content/wp-cache-config.php

Caching seems to work alright most of the time but I have reports of strange errors (old pages being served for example) and this seems like the most obvious issue to tackle.

Great plugin, by the way ?? and thanks in advance for the help.