$(function(){

  $('form#contact-form').submit(function(){
    var contact_form = $(this)
    $.post($(this).attr('action'), $(this).serialize(), function(data){ contact_form.replaceWith(data) } )
    return false;
  })

})

jQuery.ajaxSetup({ 
  'beforeSend': function(xhr) {xhr.setRequestHeader("Accept",
    "text/javascript")} 
})