urgente site

publiquei meu site qdo chamo ele ele me mostra esse erro....

Alguem pode me dizer o que pode ser ???
O erro mostrado está na linha 44 que está em negrito...

Server Error in ´/´ Application.
--------------------------------------------------------------------------------

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.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089´ or one of its dependencies. The system cannot find the file specified.

Source Error:


Line 42: <compilation debug=´false´>
Line 43: <assemblies>
[b:444ef4ab23]Line 44: <add assembly=´System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089´ />[/b:444ef4ab23]Line 45: <add assembly=´System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35´ />
Line 46: <add assembly=´System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089´ />


Source File: E:\domains\enetsystem.com.br\wwwroot\web.config Line: 44

Assembly Load Trace: The following information can be helpful to determine why the assembly ´System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089´ 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].


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