功能：鼠标移入div,背景色变为绿色，宽变小，长变大，移出恢复原状
事件：onmouseover,onmouseout
属性： background,width,height
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<title>Examples</title>
<meta name="description" content="">
<meta name="keywords" content="">
<link href="css1.css" rel="stylesheet" type="text/css"
charset="UTF-8">
</head>
<body>
<div id="div1"></div>
<script src="js1.js"> </script>
</body>
</html>
/////////////////////////css
#div1{
100px;
height:200px;
background: red;
}
//////////////////////////js
var oDiv=document.getElementById("div1")
oDiv.onmouseover=function(){
oDiv.style.background = 'green';
oDiv.style.width = '200px';
oDiv.style.height = '100px';
};
oDiv.onmouseout=function(){
oDiv.style.background = 'red';
oDiv.style.width = '100px';
oDiv.style.height = '200px';
};