So I think (or I thought) I got my hands on those viewing access levels in Joomla. But now, unless I am logged as super user, anytime I am creating a post and click on save, I got a 404 error message (page not found)

When logged in the backend as SU, I can see the topics I created (when logged as non SU) before clicking on the save button, but they are just not published. What can cause this? 

Another question about ranks. I can see there is a rank type by defaut being 'special'. The alternative is 'standard'. Is 'special' related to this defaut 'special' user group? What is the relationship? Do the permissions need to be set a specific way?

Thanks.