I'm migrating my drupal websites from a server running with Apache web server to a Nginx server. The problem is, I can't access any of my websites on the nginx server. It redirects me to a 404 error page for all websites.
Were you using clean URL's before the migration? If this is the case, than you may need to set up mod_rewrite only for nginx. I have not used the server but found this article on how to achieve the same.
Not sure if this is your problem though, although it might be.