DIV嵌套显示问题
<!DOCTYPE html>
<HTML>
<HEAD>
<TITLE>选择参培人员</TITLE><META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Content-Type" content="text/html; charset=gb2312">
<link rel="stylesheet" type="text/css" href="jquery-easyui/themes/default/easyui.css">
<link rel="stylesheet" type="text/css" href="jquery-easyui/themes/icon.css">
<link rel="stylesheet" type="text/css" href="jquery-easyui/demo.css">
<script type="text/javascript" src="jquery-easyui/jquery-1.8.0.min.js"></script>
<script type="text/javascript" src="jquery-easyui/jquery.easyui.min.js"></script>
<style type="text/css">
body{ border:0px; margin:0px; padding:0px; font-size:12px;}
#main{ overflow:hidden;width:600px;margin:0 auto; }
#left{float:left; width:300px;}
#center{float:left; width:150px;}
#right{ overflow:hidden;width:150px;}
</style>
<SCRIPT LANGUAGE="JavaScript">
function change(){
$('#main').dialog({
title: '请选择参加培训人员',
width: 650,
height: 380,
closed: false,
cache: false,
modal: true
});
}
</script>
</HEAD>
<BODY TEXT="000000" BGCOLOR="FFFFFF" >
<p align="center"><img src="jquery-easyui/themes/icons/right22.gif" class="pointer" onClick="change()"/><br/><br/></p>
<FORM METHOD=post ACTION='peixunjilu_add_s.asp' NAME='_wAddress'>
<div id="main" style="visibility: hidden;">
<div id="left"> <div class="easyui-layout" style="width:300px;height:300px;">
<div data-options="region:'west',split:true" title="请选择部门" style="width:150px;"><ul id="tt" class="easyui-tree" data-options="url:'jquery-easyui/tree_data.asp',animate:true"></ul></div>
<div data-options="region:'center',split:true" title="待选人员" style="width:150px;"><ul style="margin:0px; padding:0px; text-align:center"><select NAME="tmpleftList" id="leftList" multiple="multiple" style="width:141px;height: 265px;" ondblclick="changeValue();document.forms[0].tmprightListRef.value=selectToString(fieldAddress);" onKeyPress="if (window.event.keyCode==13){ AddClick(fieldAddress); document.forms[0].tmprightListRef.value=selectToString(fieldAddress);}"></select></ul>
</div>
</div>
</div>
<div id="center" >