<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>div</title>
<style>
#main_container{
border:1px solid #000000;
height:400px;
width:600px;
margin-right:auto;
margin-left: auto;
}
#main_container2{
width:500px;
background-color:red;
left:50%;
margin-left:-260px;
position:relative;
}
</style>
</head>
<body>
<div id="main_container">
div1
</div>
<div id="main_container2">
div 2
</div>
</body>
</html>
