Problem: form elements replaced using Ajax and lost from the form.

Here is the problem:
part of the form elements is replaced using Ajax. After this new input elements getting lost from the form so nothing can be POSTed through these input fields. But if I try to append these fields to form using appendChild - they are moved from their places in page and placed diectly after <form> tag. And sure they vanish from the browser and can't be edited.
How shall I append these fields to form to not to lose them and POST values through them?

re: Problem: form elements replaced using Ajax and lost from the form.

Post the code that you have (in code tags please). Have you set the id of the form and are you using that to append the child elements?