window.createPopup()如何背景透明
<body bgcolor=red>
<script language="javascript">
<!--
oPopup = window.createPopup();
var oPopupBody = oPopup.document.body;
oPopupBody.style.backgroundColor = "#FFFFFF";
oPopupBody.style.border = "solid #330099 3px";
oPopupBody.innerHTML = "<center>Bienvenue sur ALL HTML</center>";
oPopup.show(300, 300, 220, 30, document.body);
// -->
</script>
如何使其背景透明?