<script type="text/javascript">
var timer
function stopMove(){
clearInterval(timer)
}
function startMove(){
var div=document.getElementById('ok')
clearInterval(timer)
timer=setInterval(function(){
ok.style.width=ok.offsetWidth-1+'px' ;//理论上应该是宽度不断减少，但是实际却增长，原因在样式表中的border属性，去掉即可解决
},20)
}
</script>
<style type="text/css">
* {margin: 0;padding:0}
body {font-size: 14px;line-height: 24px;margin: 0px;padding: 0px;}
#ok{width:800px;height: 200px;background-color:darkgreen;border: 1px red solid; }
</style>
</head>
<body>
<div id="ok"></div>
<div id="ok" style="width:200px:></div>
