在javascript中怎样实现鼠标放在超链的文字上，显示出超链的的注释文字？

<html>
<head>
<title>即时出现的提示信息</title>
<style>
#div1{position:absolute;border:1 solid #3366cc;background-color:#d2e8ff;color:blue;width:100;font-size:12px}
</style>
</head>
<!--by fason-->
<body>
<script>
function document.onmousemove(){
if(event.srcElement.tagName=="A"){
var v=document.getElementById("div1")
v.style.visibility=''
v.innerHTML=event.srcElement.alt
v.style.pixelLeft=event.clientX+document.body.scrollLeft+10;
v.style.pixelTop=event.clientY+document.body.scrollTop+10
}
}
function document.onmouseout(){
if(event.srcElement.tagName=="A"){
var v=document.getElementById("div1")
v.style.visibility='hidden'
}
}
</script>
<a href=# alt="fason" >fason</a>
<div id=div1 style="visibility:hidden"></div>
</body>
</html>