这个为什么不能实现呢？
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>jQuery动画特效</title>
<style>
div{
position:absolute;
width:50px;
height:50px;
background:red;
top:50px;
left:200px;
}
</style>
<script type="text/javascript" src="http://libs.baidu.com/jquery/1.9.0/jquery.js">
$(function(){
$("#leftm").bind("click",function(){
$("div").animate({left: "-=50px"},3000);
});
$("#rightm").bind("click",function(){
$("div").animate({left: "+=50px"},3000);
});
});
</script>
</head>
<body>
<input value="左移" type="button" id="leftm"></input>
<input value="右移" type="button" id="rightm"></input>
<div></div>
</body>
</html>
