.net(C#)中用div编写的下拉菜单，如何让下拉菜单显示时在最上层。

Question

鼠标移动在文字上则显示下拉菜单，如果下边有select，listbox等控件时会将下拉菜单挡住，导致菜单显示不完整，怎样让其显示在控件的上面。 我从网上搜索了一下，说是将z-index属性值设置到最大就可以，但是我试了一下不行，不知道是不是我的用法不对，请问还有什么好的方法吗？
<DIV id="lbl1_1" onmouseover="lbl1_1.style.display='block'" style="DISPLAY: none; Z-INDEX: 1; POSITION: absolute"
onmouseout="lbl1_1.style.display='none'">
<TABLE cellSpacing="0" cellPadding="0" width="94" border="0">
<tr>
<td height="15"></td>
</tr>
</TABLE>
<TABLE class="xmenu" id="xmenu0" style="BORDER-RIGHT: #999999 1px solid; BORDER-TOP: #999999 1px solid; BORDER-LEFT: #999999 1px solid; BORDER-BOTTOM: #999999 1px solid"
height="30" cellSpacing="0" cellPadding="0" width="70" align="center" border="0">
<TBODY>
<TR vAlign="top">
</TR>
<asp:label id="lbl1_z" runat="server"></asp:label>//这里是显示的菜单内容，在后台绑定的。 </TBODY>
</TABLE>
</DIV>

Answer 1

<iframe frameborder=0 height=168px width=255px></iframe>

Answer 2

在DIV或内加Iframe就可以了

Answer 3

请问是这样吗？
<iframe   frameborder=0   height=168px   width=255px>
<DIV id="lbl1_1" onmouseover="lbl1_1.style.display='block'" style="DISPLAY: none; Z-INDEX: 1; POSITION: absolute"
                                          onmouseout="lbl1_1.style.display='none'">
                                            <TABLE cellSpacing="0" cellPadding="0" width="94" border="0">
                                                <tr>
                                                    <td height="15"></td>
                                                </tr>
                                            </TABLE>
                                            <TABLE class="xmenu" id="xmenu0" style="BORDER-RIGHT: #999999 1px solid; BORDER-TOP: #999999 1px solid; BORDER-LEFT: #999999 1px solid; BORDER-BOTTOM: #999999 1px solid"
                                                height="30" cellSpacing="0" cellPadding="0" width="70" align="center" border="0">
                                                <TBODY>
                                                    <TR vAlign="top">
                                                    </TR>
                                                    <asp:label id="lbl1_z" runat="server"></asp:label>//这里是显示的菜单内容，在后台绑定的。                                                </TBODY>
    </TABLE>
    </DIV>
</iframe>