<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
#small{
width: 200px;
height: 200px;
left: -200px;
position: relative;
background-color: red;
}
</style>
<script>
window.onload=function(){
var div1=document.getElementById('samll');
div1.onmouseover=function(){
startfun();
}
}
function startfun(){
var div1=document.getElementById('samll');
setInterval(function(){
div1.style.left=div1.offsetLeft+10+'px';
},30)
}
</script>
</head>
<body>
<div id="small"></div>
</body>
</html>
getElementById('samll');
small拼错了，大兄弟
你名字写错了，var div1=document.getElementById('samll');你自己写的small，但是变成samll，当然不对了