1.被Flash挡住
设置Flash的参数：<param name="wmode" value="opaque">
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0" width="468" height="60"><param name="movie" value="http://pepsi.flash8.net/pepsi46860.swf">
<param name="wmode" value="opaque"><param name="quality" value="high"><embed src="http://pepsi.flash8.net/pepsi46860.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="468" height="60"></embed></object>
<div style="position:absolute;left:150;top:50;width:100px;height:50px;background:green">
</div>
或者用<param name="wmode" value="transparent">
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0" width="468" height="60"><param name="movie" value="http://pepsi.flash8.net/pepsi46860.swf">
<param name="wmode" value="transparent"><param name="quality" value="high"><embed src="http://pepsi.flash8.net/pepsi46860.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="468" height="60"></embed></object>
<div style="position:absolute;left:150;top:50;width:100px;height:50px;background:green">
</div>
2.被图片挡住
这个估计是因为图片也放在层中，而图片所在层的Z轴索引值比该层大，所以被挡住，解决办法是更改该层的Z轴索引值至比图片层大。
<div style="position:absolute;left:0;top:20;z-index:2;background:red;width:120px;height:70px">
1<img src="/Article/UploadFiles/200602/20060208094014220.gif">
</div>
<div style="position:absolute;left:50;top:50;z-index:2;background:green;width:120px;height:70px">
2<img src="/Article/UploadFiles/200602/20060208094014220.gif">
</div>
<div style="position:absolute;left:90;top:80;z-index:2;background:blue;width:120px;height:70px">
3<img src="/Article/UploadFiles/200602/20060208094014220.gif">
</div>
3.被表单控件挡住
这个目前还没有完美的解决方法，一般都是在设计排版时就尽量避免这种情况，如果是万不得已，就在层经过表单控件时让表单控件隐藏，过后再让它显示：
<button onClick="oSelect.style.display='none';oLayer.style.display='inline'">显示层隐藏下拉选项</button><button onClick="oSelect.style.display='inline';oLayer.style.display='none'">显示下拉选项隐藏层</button>

<div style="position:absolute;left:0;top:50;z-index:2;background:red;width:120px;height:50px">
z-index:1<select id="oSelect"></select>
</div>
<div id="oLayer" style="position:absolute;left:30;top:60;z-index:2;background:green;width:120px;height:70px;display:none">
z-index:2<img src="/Article/UploadFiles/200602/20060208094014220.gif">
</div>
当然还有用优先级别较高的控件来代替层的方法解决，但控件并非是每台机器上都有安装，而且控件的可定制性也差，也就是常说的兼容性问题：
hhctrl.ocx
<OBJECT id=hhctrl type="application/x-oleobject" classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" codebase="<I>file:</I>hhctrl.ocx#Version=4,0,0,24" width=80 height=20>
<PARAM name="Command" value="Related Topics, MENU">
<PARAM name="Button" value="Menu">
<PARAM name="Item1" value="[X-Eyes];http://x-lover.com/forums/">
<PARAM name="Item2" value="闪客之吧;http://www.flash8.net">
<PARAM name="Item3" value="零刻联盟;http://www.linkmeng.com/">
<PARAM name="Item4" value="蓝色理想;http://www.blueidea.com/">
<PARAM name="Item5" value="<a href="http://www.5d.cn">5D多媒体</a>;http://www.5d.cn">
</OBJECT>
<select></select>
window.createPopup()窗口(需要IE5.5+支持)
<SCRIPT>
var oPopup = window.createPopup();
function showPopupWin(){
var oPopBody = oPopup.document.body;
oPopBody.style.backgroundColor = "green";
oPopup.show(50, 120, 180, 65,document.body);
}
</SCRIPT>
<BUTTON onclick="showPopupWin()">Click Me!</BUTTON><select></select>
<iframe src="index.asp"></iframe>