title: Configuration error: System.Web.Helpers
body: <p>I deployed a site to a server and I get this error.  Why do I get this?</p>
  
  <pre><code>Configuration Error 
  Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. 
  
  Parser Error Message: Could not load file or assembly 'System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
  
  Source Error: 
  
  
  Line 16:       &lt;assemblies&gt;
  Line 17:         &lt;add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
  Line 18:         &lt;add assembly="System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
  Line 19:         &lt;add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
  Line 20:         &lt;add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
  
  Source File: C:\&lt;path&gt;\web.config Line: 18 
  
  Assembly Load Trace: The following information can be helpful to determine why the assembly 'System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded.
  
  
  WRN: Assembly binding logging is turned OFF.
  To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
  Note: There is some performance penalty associated with assembly bind failure logging.
  To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].
  </code></pre>