Does your search page display a list of results, or does it redirect to the best result? If the former, I'd say that a list of zero is still a valid search resu

Does your search page display a list of results, or does it redirect to the best result? If the former, I'd say that a list of zero is still a valid search results 'document', and should therefore return a 200. But the latter could certainly return a 404, although I doubt that's how your search actually works :)