AJAX: Unknown server tag 'asp:ScriptManager'

 

add the <Pages>...</Pages> given in the frist post above to <System.Web> element in the web.config.
something like this:

..
< System.Web >


< pages >

< controls >

< add  tagPrefix ="asp"  namespace ="System.Web.UI"  assembly ="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"   />

</ controls >

</ pages >
</ System.Web >