JavaScript exception - can't figure it out

I have the following code in the middle of my html:

<script type="text/javascript">
   CKEDITOR.config.customConfig = '`img`/ckeditor/ckeditor_config.js';
   CKEDITOR.replace(document.CreateItem.Comments);
</script>

<TD COLSPAN="3">
   <TEXTAREA CLASS="valueEditable ckeditor" NAME="Comments" ID="Comments" ROWS="12" COLS="60" WRAP="SOFT" onChanged="markDirty()"></TEXTAREA>
   <script type="text/javascript">
   CKEDITOR.replace('Comments',
   {
      toolbar :
      [
         ['Bold','Italic','Font','FontSize']
      ]
   });
   </script>
</TD>

Using Firebug I get the following error:

uncaught exception: [CKEDITOR.editor.replace] The element with id or name "undefined" was not found.

I am not sure what to make of this. I just followed the instructions in the documentation. I know next to nothing about JavaScript!