your closing the form inside the form tag by adding a "/" at the end:
<form name="ajax-form" id="ajax-form" action="" method="post" enctype="multipart/form-data" />
using the "/" to close the tag is only appropriate for tag types that don't have a companion closing tag such as the line break tag:
<br />
it should not be used for elements that do have companion closing tags like the form tag.