部分具体代码如下：
<script type="text/javascript">
var size=20;
function changeStyle(state){
var a1=document.getElementById('link1');
if(state=='up'){
size+=5;
a1.style.fontSize=size+'px';
}else{
size-=5;
a1.style.fontSize=size+'px';
}
}
</script>
</head>
<body>
<p id="link1"> jagbfieabv</p>
<input type="button" value="bigger" onclick="changeStyle('up')" />//放大按钮
<input type="button" value="smaller" onclick="changeStyle('down')" />//缩小按钮
</body>
当点击放大按钮时，字体也会放放大，同样，再点击缩小按钮，字体也会缩小，