<form name="form1">
      <input name="input1"></input>
      <textarea name="textarea1" onkeyup="count(event)"></textarea>
    </form>

    <script language="JavaScript">
      var max = 25;

      document.form1.input1.value = max;
      document.form1.textarea1.focus();

      function count(e) {
        if (!e.which) keyCode = event.keyCode; // ie5+ op5+
        else keyCode = e.which; // nn6+

        if (document.form1.textarea1.value.length<max+1)
            document.form1.input1.value = max-document.form1.textarea1.value.length;
        else {
          document.form1.textarea1.value = document.form1.textarea1.value.substring(0,max);
          document.form1.input1.value = 0;
        }
      }
    </script>