Select和DIV层的叠加优先级别

$("body").append("<div id='Search_Layer'><iframe  src='' style='border:0px; padding:0px; margin:0px; solid red; width:600px; height:200px; z-index:12; filter:progid:DXImageTransform.Microsoft.Alpha(style=0,opacity=0); background-color:red;'></iframe>"
+"<ul class='Search_Title' style='margin-top:-200px;'>"
+" <li class='sTitle'>职位类型</li><li class='sClose'></li>"
+"</ul>"
+"<ul id='Search_tianjia' style='margin-top:-160px;'>"
+" <li id='Search_tianjiaBtn'><img id='clear' src='images/clear.png'><img id='ok' src='images/ok.png'></li>"
+"</ul>"
+"<ul class='Search_Box' style='margin-top:-100px;'></ul></div>"
+"<ul id='innerBox'></ul>");

来源：http://www.secn.com.cn（尚E导航网址）