I've erased some articles in Joomla (1.7). They're invisible in article manager, but they are visible on the website. How do i remove them completely? When I see, the "Super User" account even has not permissions to edit them (no edit icon).

You're most likely drenched in as super admin around the frontend. That method for you to still see articles that are within the trash (not fully erased). If you would like do remove them permanently, change to the garbage view and remove them.