请问，如何在线选择文字大小，参照~~~

1<style>   
2.b{font-size:20pt;}   
3.s{font-size:10pt;}   
4</style>

1<p class="s" id="woyingjie">woyingjie</p>

1<a href="#" onclick="document.all.woyingjie.className='b'">大</a>

1<a href="#" onclick="document.all.woyingjie.className='s'">小</a>

1<script language="JavaScript">   
2<!--   
3function doZoom(size){   
4document.getElementById('zoom').style.fontSize=size+'px'   
5}   
6// -->   
7</script>

1<a href="javascript:doZoom(20)">大</a>

1<a href="javascript:doZoom(16)">中</a>

1<a href="javascript:doZoom(12)">小</a>

1<div id="zoom">woyingjie</div>