根据输入的值即时改变textarea内文字的大小

<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>新建网页 1</title>
</head><body>
<p>Font Size: <input type="text" name="T1" size="20" value="10" onkeyup="javascript:if( !isNaN(this.value)) document.all.S1.style.fontSize=this.value" >   <input type=button value=" OK " > </p>
<textarea rows="20" name="S1" cols="56" style="font-size:10px" id="S1">abcdedfffffffffffffffffffsssasdfasdfadsfasdf</textarea>
</body>