ASP.NET Ajax Technology in New Version Browser (IE9)

Using an old version of Ajax can be not compatible with Internet Explorer 9.

i.e: problem with popup windows 

Adding the line below in a master page, for example, fixes that problem 

<%@ Master Language="VB" CodeFile="MasterPage.master.vb" Inherits="MasterPage"     %>

<meta http-equiv="X-UA-Compatible" content="IE=100" > <!-- IE9 mode -->

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>