Yesterday I was working on a project which had the AJAX Extensions in use. It’s primarily a .NET 2.0 application and I had .NET Framework 3.5 SP 1 installed on my system. It was working normally and all of a sudden I got this error that: Unknown server tag ‘asp:ScriptManager’
It was strange because every thing was working and I had the reference to the AjaxControlToolkit.dll.
I found out that by adding the section below to the <system.web> node in the web.config solves the problem:-
<pages>
<controls>
<add tagPrefix=”asp” namespace=”System.Web.UI” assembly=”System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35″ />
</controls>
</pages>
Imran Akram's Blog 
Thanks man, it was really helpful ๐
ูู ุชุนู ู ู ุนู ๐ฆ
Good.. Thanks
Very nice You saved my time a lot Thanks a lot if you need any technical help Please reach me
I do what you say but another error appeared , the error is :
Could not load file or assembly ‘System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies. The system cannot find the file specified.
Source Error:
[No relevant source lines]
That’s weird. I think its just because you’re missing the reference to AjaxControlToolkit.dll. If not try adding it to the GAC.
Update under control tag in web.config like this
(please check the version).
Thanksssss a tonn ๐
Thanx alot.
thankx
i have the same lines specified by you. The dashboards were working fine but after installation of certificate it shows this error. Any help would be appreciated
I have the same lines as specified by you. the dashboards were working fine but after the installation of the SSL certificate on the SharePoint server the dashboards throw this error. Any help would be appreciated