<script type="text/javascript">
<!--
var nom;
function inserticon(nom){
    var temps;
    temps=document.getElementById('form1').comm.value;
    temps=temps+''+nom+''
    form1.comm.value=temps;
}
//-->
</script>
 
<form id="form1" method='post' action="gastboek.php">
<div>
<table width="100%">
 <tr>
  <td>Naam</td>
 </tr>
 <tr>
   <td><input class="login2" type='text' size='22' name='naam' value='' /></td>
 </tr>
 <tr>
   <td>E-mail*</td>  
   <td><table border="1">
      <tr>
      <td align="center"><a onclick='inserticon(":-)" );'><img src='images/smileys/smiley1.gif' alt="" /></a>&nbsp;</td>
      <td align="center"><a onclick='inserticon(":-(" );'><img src='images/smileys/smiley2.gif' alt="" /></a>&nbsp;</td>
      <td align="center"><a onclick='inserticon(":-$" );'><img src='images/smileys/smiley3.gif' alt="" /></a>&nbsp;</td>
      <td align="center"><a onclick='inserticon(":-D" );'><img src='images/smileys/smiley4.gif' alt="" /></a>&nbsp;</td>
      <td align="center"><a onclick='inserticon(";-)" );'><img src='images/smileys/smiley5.gif' alt="" /></a>&nbsp;</td>
      <td align="center"><a onclick='inserticon(":-P" );'><img src='images/smileys/smiley6.gif' alt="" /></a>&nbsp;</td>
      <td align="center"><a onclick='inserticon("8-)" );'><img src='images/smileys/smiley7.gif' alt="" /></a>&nbsp;</td>
     </tr>
   </table></td>
  </tr>
  <tr>
     <td><input class="login2" type='text' size='22' name='email' value='' /></td>
  </tr>
</table>
 
<table width="100%">
   <tr>
       <td align="center"><textarea class="login2" name='comm' rows='10' cols='83%' value=""></textarea></td>
   </tr>
      <tr>
        <td align="center"><input class="button1" type='submit' value='Schrijf' /></td></tr>
</table>
</div>
</form>

form1 is not defined
http://jerome.monprojet.info/Nivo/gastboek_schrijf.php
Line 79