ti posto un esempio che ho salvato nell' hdd
codice:
<script type="text/javascript">
function textCounter(field, countfield, maxlimit) {
if (field.value.length > maxlimit)
field.value = field.value.substring(0, maxlimit);
else
countfield.value = maxlimit - field.value.length;
}
</script>
<form>
( Puoi mettere 125 caratteri. )
<textarea name=message wrap=physical cols=28 rows=4 onKeyDown="textCounter(this.form.message,this.form.remLen,125);" onKeyUp="textCounter(this.form.message,this.form.remLen,125);"></textarea>
<input disabled="disabled" type="text" name="remLen" size="3" value="125">caratteri rimanenti
</form>
ciao