Correct HTTP status code for existent resource, but non-existent entity?

Question

Say the client is requesting the following URL:

/user-details?user=123

If /user-details was a non-existing resource, the corre

Answer 1

Try 422 which is used in WebDav? See http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

For me 404 status is ok too (better normed actually), 400 is too vague.