IE6下div会被ListBox、DropDownList遮住的处理办法
把一个空的Iframe放到DIV里面就好了，不能包着的自己的控件，并且宽度和高度要和DIV一样
<div id='divForm' style='display: none; position: absolute; z-index: 1000; background-color: White'>
<CopyControl:CopyDiv runat="server" ID="CopyControl">
</CopyControl:CopyDiv>
<IFRAME width="300px" height="170px" style="position:absolute; top:0px; z-index:-1; border-style:none; border-width:0px; border:0px">
</IFRAME>
</div>
<CopyControl:CopyDiv runat="server" ID="CopyControl">
</CopyControl:CopyDiv>
<IFRAME width="300px" height="170px" style="position:absolute; top:0px; z-index:-1; border-style:none; border-width:0px; border:0px">
</IFRAME>
</div>
