What I do is send messages as part of the page, fall into hidden tags <span>with "id" values made from property names.
Ajax- .
ajax, , - . (.. , ), . , , , - (, " , " validation.addressForm "") )
: jQuery:
$.get('/fetchProperty', { property: 'firstNameMissing' }, function(propValue) {
$('#errMsg').text(propValue);
}, "text/plain");
ajax, XMLHttpRequest.