下拉框把弹出菜单的层挡住了怎么解决啊?请高手帮忙一下..谢谢

下拉菜单把弹出菜单的层挡住了.怎么解决啊?我的代码是:

<SCRIPT language="JavaScript">
<!--

function makevisible(cur,which){

if (which==0)

cur.filters.alpha.opacity=150

else

cur.filters.alpha.opacity=80

}
//-->
</SCRIPT>
<style type="text/css">
<!--
.style1 {color: #FFFFFF}
.style6 {
font-size: 13px;
color: #000000;
}
-->
</style>

<table width="100%" height="39" border="0" align="center" cellpadding="0" cellspacing="0">
<form name="fum" method="post" action="search.asp">
<tr>
<td width="1%">　</td>
<td width="12%">
<!--#include file="area.asp"--> </td>
<td width="5%">
<%
sql = "select * from sort_shop where layer=0 order by orders desc"
rs.open sql,conn,1,1
if rs.eof and rs.bof then
response.write "请先添加栏目"
response.end
else
%> </td>
<td width="12%"><select name="class1" size="1" onChange="changelocation(document.fum.class1.options[document.fum.class1.selectedIndex].value)">
<option value="0" selected>在所有分类中...</option>
<%do while not rs.eof
%>
<option value="<%=trim(rs("id"))%>"><%=trim(rs("sname"))%></option>
<%
rs.movenext
loop
end if
rs.close
%>
</select></td>
<td width="5%">
</div></td>
<td width="1%">&nbsp; </td>
<td width="38%">
<input name="keys" type="text" size="50" maxlength="50" /></td>
<td width="17%"><INPUT id=lx_1 type=radio CHECKED value=1 name=lx>
<span class="">
<font color="#FFFFFF">
<LABEL for=lx_1>找商家</LABEL></font>
</span>
<INPUT id=lx_2 type=radio value=2 name=lx>
<span class="">
<font color="#FFFFFF">
<LABEL for=lx_2>找优惠</LABEL></font>
</span> </td>
<td width="6%">
<input name=Submit type=submit class="" onClick="javascript:return gosearch()" value=" 搜 索 " ></td>
<td width="3%">&nbsp; </td>
</tr>
</form>
</table>

在线等各位高手帮忙解决一下.谢谢...