opera DOM不理display:none的元素

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
</HEAD><BODY>
<div id="frames">
<div class="frame" id="7"><div class="titlebar" onmousedown="moveEle(event, this.parentNode);"></div><img src="01.gif" /><span><span>Title 7</span></div>
<div class="frame" id="8"><div class="titlebar" onmousedown="moveEle(event, this.parentNode);"></div><img src="02.gif" /><span>Title 8</span></div>
<div id="moveBox"></div>
<div id="clearFrame" style="clear:both;">&nbsp;</div>
</div>
<script>
alert(document.getElementById("frames").childNodes.length);
</script>
</BODY>
</HTML>这里在op下只有2个节点