Receiving Parser Error saying it could not load file or assembly, I checked and it's using the correct version though?

I'm trying to run an ASP web app but it's throwing a 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: Could not load file or assembly 'Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

I Google'd this message and all of the threads I could find were people saying that the version number that it's referencing is incorrect. I checked the compiler version in the web.config file and it's indeed using version 2.0.0.0. Where am I going wrong?

The source error looks like this:

Line 1:  <%@ Page Title="Test Page" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="TestPage.aspx.cs" Inherits="TestModel.TestkModel" Runat="server" Debug="true"%>
Line 2:  
Line 3:  <asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">

with Line 1: being the line highlighted in red.