关于js问题 请求大家帮忙
程序代码：<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www. xmlns="http://www. http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>显示、隐藏弹出层的例子</title>
<style type="text/css">
body{
color:#008000;
font:12px/1.5 arial;
}
a{
color:#0B59B2;
margin:0 8px;
}
#box{
position:absolute;
width:230px;
height:60px;
background:#F5F9FA;
border:2px solid #95B5D5;
display:none;
}
</style>
<script type="text/javascript">
window.onload = function ()
{
var aA = document.getElementsByTagName("a");
var oBox = document.getElementById("box");
var timer = null;
var i = 0;
for (; i < aA.length; i++)
{
aA[i].onmouseover = function ()
{
clearTimeout(timer);
var oParent = this.parentElement || this.parentNode;
oBox.style.top = pageY(this) + this.offsetHeight + 5 + "px";
oBox.style.left = pageX(oParent) + "px";
oBox.style.display = "block"
};
aA[i].onmouseout = oBox.onmouseout = function ()
{
timer = setTimeout(function ()
{
oBox.style.display = "none"
}, 300)
};
oBox.onmouseover = function ()
{
clearTimeout(timer);
}
}
};
function pageX (elem)
{
return elem.offsetLeft + (elem.offsetParent ? arguments.callee(elem.offsetParent) : 0)
}
function pageY (elem)
{
return elem.offsetTop + (elem.offsetParent ? arguments.callee(elem.offsetParent) : 0)
}
</script>
</head>
<body>
<p>作者：<a href="javascript:;">swiss原子弹</a>发表日期：211-8-17 21:56:00</p>
<p>作者：<a href="javascript:;">可乐马驹</a>发表日期：211-8-17 21:56:00</p>
<p>作者：<a href="javascript:;">网友网友love</a>发表日期：211-8-17 21:56:00</p>
<div id="box"></div>
</body>
</html>其中
var aA = document.getElementsByTagName("a");
指定的是a标记 我想这样<p>作者：<a href="javascript:;">swiss原子弹</a>发表日期：211-8-17 21:56:00</p>给a标记定义一个id
<p>作者：<a id="pop" href="javascript:;">swiss原子弹</a>发表日期：211-8-17 21:56:00</p>这样怎么做才能是这段程序运行成功
