When a content has been deleted, it's better to return a 410 error code than a 404.

It allows google and others search engine to understand that the content has existed and has been definitly removed and it forces the URL to be unindexed from the search engine faster.

The 404 error code should only be returned for contents which have never existed

eZPublish should make the difference beetween the both case in order to improve its SEO compliancy.