1. Modal 창에서 PostBack ... 당연히 가능합니다...
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Modal</title>
<script type="text/javascript">
window.name = "myModal"; // form 의 target 과 일치....
</script>
</head>
<body>
<form id="form1" runat="server" target="myModal"> <!-- form 에 target 추가... -->
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
</form>
</body>
</html>
출처 : http://www.taeyo.net/Forum/Content.aspx?SEQ=26106&TBL=ASPNET&PGN=1