Some dialog behavior. Would it be better for the dialog to be an iframe? Depends...

dialog.js

var dialog = $('<div />').appendTo(document.body);

// Close the dialog when the user clickes out of it.
$('body').on('mousedown', function(){ dialog.remove(); });
dialog.on('mousedown', function(e){
  // Don't let clicks bouble-up to the body and remove the dialog.
  e.stopPropagation();
});

// Open links in the dialog
dialog.on('click', 'a', function(e){
  e.preventDefault();
  dialog.load(this.href);
});

// Submit forms within the dialog (Not complete, or probably safe).
dialog.on('click', 'form input[type="submit"]', function(e){
  e.preventDefault();
  var form = $(this).closest('form');
  $.ajax({
    type: 'POST',
    url: form.attr('action'),
    data: form.serialize(),
    complete: function(xhr, status){
      dialog.html(xhr.responseText);
    }
  });
});