Just looked this up and you're right: in Firefox 3.6, there's a bug where the XMLHttpRequest response body won't be populated by Firefox if the status code is 4

Just looked this up and you're right: in Firefox 3.6, there's a bug where the XMLHttpRequest response body won't be populated by Firefox if the status code is 400. Seems like a little-known bug that has been vaguely referenced elsewhere. http://bugs.jquery.com/ticket/7868 http://bugs.jquery.com/ticket/7868 http://stackoverflow.com/questions/5884286/jquery-ajax-with-non-200-responses http://stackoverflow.com/questions/5884286/jquery-ajax-with-...