oups i think i find it here http://ez.no/community/bugs/extension_with_settings_override_ini_append_breaks_ezp_override_system/template_overriding
1. settings/override.ini - the main overrides (we don't recomend to change these settings).
2. settings/siteaccess/<your_siteaccess>/override.ini.append.php - current siteaccess overrides.
[[[[3. extension/<your_extension>/settings/override.ini.appens.php - extension overrides.]]]]
4. settings/override/override.ini.append.php - global overrides.