HTML:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<link type="text/css" href="09.css" rel="stylesheet"/>
<script type="text/javascript" src="jquery.js"></script>
<title></title>
</head>
<body>
<h1>wo men</h1>
<p>cfjdsmc edvc ewrd csd wrvc d 2e34efrew8r934efc cred ewfced
vefwid cfer fd 3ew fcxdwdkjfdke fewf dewkdse fcedwfewdfcs
fre dfc ed fcejfoklew ferf
defedefcd</p>
<input type="button" id="big" value="放大"/><br />
<input type="button" id="small" value="縮小"/>
<script type="text/javascript">
$("input").click(function(){
var t = $("p").css("font-size")
var t1 = parseInt(t, 10)
var unit = t.slice(-2)
var name1 = $(this).attr("id")
if(name1 == "big"){
t1 += 2
}
else if(name1 == "small"){
t1 -= 2
}
$("p").css("font-size", t1+unit)
})
</script>
</body>
</html>