看起来像您部署的应用程序没有ASP.NET MVC 3安装服务器。如果你不希望在服务器，你也可以的仓部署您的应用程序。

I deployed a site to a server and I get this error. Why do I get this?

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:       <assemblies>
Line 17:         <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
Line 18:         <add assembly="System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
Line 19:         <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
Line 20:         <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />

Source File: C:\<path>\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].

Looks like the server on which you deployed the application doesn't have ASP.NET MVC 3 installed. If you do not want to install ASP.NET MVC 3 on the server you could also bin deploy your application.