请问为什么我在Popup中的事件无法响应？

Question

this way: 
----------------------
<script language="javascript">
<!--
var popup;
function showPopup(src){
    popup=null;
    popup=window.createPopup();
    popup.document.body.backgroundColor = "lightyellow";
    popup.document.body.style.border = "solid black 1px";
    var tableCounter=popup.document.createElement("TABLE");
    tableCounter.cellSpacing=2;
    tableCounter.cellPadding=2;
    tableCounter.style.cursor = "default";
    var newRow = tableCounter.insertRow();
    var newCell = newRow.insertCell();
    newCell.width = 10;
    newCell.height = 10;
    newCell.style.fontSize = "5pt";
    newCell.style.border = "1px solid #000000";
    newCell.style.backgroundColor = "#FFFFFF";
    newCell.innerHTML = "&nbsp;Yeefly Out";
    newCell.attachEvent("onmouseover",alertMe);
    popup.document.body.appendChild(tableCounter);
    popup.show(event.clientX, event.srcElement.height, event.clientX, event.clientY, src);
}
function alertMe()
{
alert("hello World");
}
document.body.onclick = function(){showPopup(document.body)};
//-->
</script>