hi, i developed a web application it is working fine in local server. when i uploaded the site in online when i click on some of the buttons i am getting this error. I am using master page, but i am not place the scriptmanager in master page,i place the scriptmanager tag in every page. It is working fine in local server but it is giving error in online. please can u help me. Thank you

Parser Error
Description: An error occurred during the parsing of a resource required to
service this request. Please review the following specific parse error details
and modify your source file appropriately.

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

Source Error:

Line 9:  <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
Line 10: 
Line 11:     <asp:ScriptManager ID="ScriptManager1" runat="server">
Line 12:     </asp:ScriptManager>
Line 13:          <asp:UpdatePanel id="UpdatePanel2" runat="server" UpdateMode="Conditional">