Lo script di badaze si puo` semplificare e trasformare facilmente in crossbrowser:
codice:
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function checkChars(aTextarea) {
  var max = 300;
  var a = aTextarea.value;
  document.getElementById('conta').innerHTML = a.length;
 
  if (a.length > max) {
    //alert('Too much characters');
    aTextarea.value = a.substr(0,max);
    return false;
  }
  return true;
}
//-->
</script>
</head>
<body>
<textarea cols="50" rows="20" id="text" onkeyup="checkChars(this)"></textarea>

<div id="conta">&amp;nbsp;</div>
</body>