the error is occurring because your form tag does not have a name attribute.
change:
<form action="" method="post" enctype="multipart/form-data" id="form1">
to ;
<form action="" method="post" enctype="multipart/form-data" name="form1" id="form1">
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.