Unknown Server Tag ASP:script Manager error in IIS 7 ?

Hello All,

I am using visual studio 2010 , I Found AJAX Controls already available in my tool box without installing the AJAX.I Added Update Progress tag and It executed well in my local system.But while executing the Page in IIS 7 displays the following error.

Parser Error Message: Unknown server tag 'asp:ScriptManager'.

Whats the Issue.Can anyone shed some light on this issue.Urgent.

Thanks in Advance