$_MESSAGE$

<div onKeyUp="chklen()">
  $_MESSAGE$
  </div>
  Осталось символов: <input name="fcounter" type="text" class="codeButtons" size="6" value="20000" readonly="true">

<script language="JavaScript" type="text/javascript">
  function chklen()
  {
  max_limit=20000;

  str = document.addform.message.value;
  len = str.length;

  if (len > max_limit)
  {
  str = str.substring(0,max_limit);
  len = str.length;
  document.addform.message.value = str;
  }

  document.addform.fcounter.value = (max_limit - document.addform.message.value.length);

  while ( document.addform.fcounter.value<0)
  {
  document.addform.message.value = str.substring(0,len-1);
  str = document.addform.message.value;
  len = str.length;
  document.addform.fcounter.value = (max_limit - document.addform.message.value.length);
  }
  }
  </script>