Error regarding AjaxControlToolKit

When I run the page, I get the following parsing error.

Analyzer error

Description. An error occurred while parsing a resource required to service this request. Review the following parsing details and modify the original file accordingly.

Parser error message: Could not load file or assembly "AjaxControlToolkit, Version = 1.0.10618.0, Culture = neutral, PublicKeyToken = 28f01b0e84b6d53e" or one of its dependencies. The located assembly manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Source error:

Line 1: <% @Page Language = "vb" AutoEventWireup = "false" CodeBehind = "AppointmentSchedule.aspx.vb" Inherits = "AFKLogin.AppointmentSchedule" MasterPageFile = "~ / Login / PatientMaster.Master"%>

Line 2:

Line 3: <% @ Register Assembly = "AjaxControlToolkit" Namespace = "AjaxControlToolkit" TagPrefix = "cc1"%>

Source file: /Allforkids/Login/AppointmentSchedule.aspx Line: 1

Assembly loading trace. The following information may be helpful in determining why the assembly "AjaxControlToolkit, Version = 1.0.10618.0, Culture = neutral, PublicKeyToken = 28f01b0e84b6d53e" could not be loaded.

WRN: Assembly binding registration is disabled. To enable Build Failure Logging, set the registry value [HKLM \ Software \ Microsoft \ Fusion! EnableLog] (DWORD) to 1. Note. There is some performance limitation related to the assembly binding failure protocol. To disable this feature, delete the registry value [HKLM \ Software \ Microsoft \ Fusion! EnableLog].

Version Information: Microsoft .NET Framework Version: 2.0.50727.3082; ASP.NET Version: 2.0.50727.3082

How can I fix this?