codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Untitled Document</title>
<script type="text/javascript">
function textCounter(field, countfield, maxlimit) {
	var conta = (maxlimit - field.value.length);
	if(conta<=0){
			countfield.value = 0;
			document.getElementById('minimo').className='min';
			document.getElementById('minimo').innerHTML='Limite minimo: 300 caratteri raggiunto.';
			
	}else{
		countfield.value = conta;
		document.getElementById('minimo').className='default';
		document.getElementById('minimo').innerHTML='Limite minimo: 300 caratteri.';
		
}
}    
</script>
<style type="text/css">
.min{
	color: #990;
	font-weight: bold;
}
#minimo{
	font-size: 12px;
	float: left;
	font-family: Verdana, Geneva, sans-serif;
	font-size: 12px;
	float:left;
}
.default{color:#C00;font-weight:normal;}
</style>
</head>

<body>
<div id="main">
<form action="" method="get"><textarea name="bodytext" rows="10" cols="60" id="bodytext" onkeyup="textCounter(this,this.form.remLen,300);" "></textarea>

<input readonly="readonly" type="text" name="remLen" size="3" maxlength="3" value="300" style="float:left;"><div id="minimo" class="default">Limite minimo: 300 caratteri.</div></form>
</div>
</body>
</html>