When a requests returns a 4xx as status code, the specified "error" handler should be called, because 4xx status codes indicate an error: "The 4xx class of status code is intended for cases in which the client seems to have erred" from RFC 2616[1]

[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

$.ajax({
	url: some/url.html, // This page should return, for example, a 403 Permission denied
	error: function() {
		console.log('Error');
	},
	complete: function(jqXHR, textStatus) {
		if(parseInt(jqXHR.status) === 403) {
			console.log('Permission denied');
		}
	}
});

Expected console output:

Permission denied.
Error.

Actual output:

Permission denied.