JS 鼠标事件onmouseover：鼠标移到某元素之上;onmouseout：鼠标从某元素移开

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
        <script type="text/javascript">
            window.onload=function(){
                var img=document.getElementsByTagName("img")[0];
                img.onmouseover=function(){
                    document.getElementById("msg").innerHTML="over...";
                }
                img.onmouseout=function(){
                    document.getElementById("msg").innerHTML="out...";
                }
            }
        </script>
    </head>
    <body>
        <img src="image/ad-03.jpg" />
        <div id="msg"></div>
    </body>
</html>

代码验证图片