div层遮住了Iframe,iframe中的内容无法操作！

yes_no57111510 2009-10-30 03:44:52

代码如下：
<body>
<table>
<tr>
<td>

<div class="menu">

<div class="main_menu">

<div class="main_menu_left">
<ul id="menu_first">
<li onmouseover="secBoard(0)" class="sec2"><a href="#">aa</a></li>
<li onmouseover="secBoard(1)" class="sec1"><a href="#">bb</a></li>
</ul>
</div>
</div>

<div class="sub_menu">

<div class="sub_menu_left">
<div id="main">
<div class="block">
<ul>
<li id="summenu1"><a id="seconda1" href="#" target="mainframe" >a1</a>
<ul>
<li><a href="#" target="mainframe" >a11</a></li>
<li><a href="#" target="mainframe" >a12</a></li>
<li><a href="#" target="mainframe" >a13</a></li>
<li><a href="#" target="mainframe" >a14</a></li>
<li><a href="#" target="mainframe" >a15</a></li>
</ul>
</li>
<li id="summenu2"><a id="seconda2" href="#" target="mainframe">a2</a>
<ul>
<li><a href="#" target="mainframe">a21</a></li>
<li><a href="#" target="mainframe">a22</a></li>
</ul>
</li>

</ul>
</div>
<div class="unblock">
<ul>
<li><a href="#">b1</a></li>
<li><a href="#">b2</a></li>
<li><a href="#">b3</a></li>
<li><a href="#">b4</a></li>
</ul>
</div>
</div>
</div>


</td>
</tr>
<tr>
<td style=" width: 100%; height: 440px;">

<div style="z-index:-1; position: relative;">
<iframe frameborder="0" scrolling="auto" name="mainframe" style=" z-index:-1; border-style:none; width: 990px; height: 440px; position: absolute;" src="Default.aspx"></iframe>
</div>
</td>
</tr>
</table>
</body>

选中链接后，Iframe中的内容无法操作，好像是被层遮住的效果一样，
希望高手帮忙！谢谢

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