C# - Register Ajax Tool Kit To SharePoint 2010?

I've tried to use Ajax Control Tool Kits on SharePoint 2010 Web Site, but Im having some trouble with registration. I've searched a lot on google for a solution. I've found some ways, but my problem is not solved. When I open my web site, still getting registration error.The problem is registration of Ajax Tool Kit. Here is my steps.1 - Downloaded Ajax Control Tool Kit latest version.2 - Added following line to my page

<%@ Register Assembly="AjaxControlToolkit, Version=3.0.30930.28736, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>

3 - Added following line to my master page (v4.master)

<%@ Register Assembly="AjaxControlToolkit, Version=3.0.30930.28736, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>

4 - Replaced this tag

<asp:ScriptManager>

with

<ajaxToolkit:ToolkitScriptManager>

but problem not solved.. Still getting same registration error. I need your suggestions about implementing Ajax Control Tool Kits on Share Point 2010.