title: HTTP status code for bad data
body: <p>What HTTP status code should I return when a client posts bad data (e.g. a string when integer was expected)?</p>
  
  <p>I've been using 400 Bad Request, but as I read over the HTTP docs that seems more applicable to HTTP protocol errors.</p>
  
  <p>I'd like to use a status code so that Flash and AJAX clients can distinguish between success, bad data, and server error without having to parse a response.</p>