Using IFRAME to solve the conflict between the dropdown frame and the layer

Solve the problem of pull down: I made a pull-down menu with DW, but ran to the bottom of the list item of form, please help solve it, please see the problem diagram as follows:

Problem solving: Because the priority between the layer and the Drop-down box is: the dropdown box > layer, the above problem will occur because of the priority order in the display. (if several elements are layers, we can set it by the layer's Z-index property): Give the layer a higher priority than the dropdown box (IFRAME) to solve the problem! The specific resolution code is as follows:

<div id= "Menu" style= "Position:absolute; Visibility:hidden; top:20px; left:20px; width:100px; height:200px; Background-color: #6699cc; " >
<table>
<tr><td>item 1</td></tr>
<tr><td>item 2</td></tr>
<tr><td>item 3</td></tr>
<tr><td>item 4</td></tr>
<tr><td>item 5</td></tr>
</table>
<iframe src= "Javascript:false" style= "Position:absolute; Visibility:inherit; top:0px; left:0px; width:100px; height:200px; Z-index:-1; Filter= ' Progid:DXImageTransform.Microsoft.Alpha (style=0,opacity=0) '; ></iframe>
</div>

<a href= "#" >menu</a>

<form>
<select><option>a form Selection list</option></select>
</form>