Orchard/src/Orchard.Web/Modules/Orchard.Users/Web.config

<?xml version="1.0"?>

<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      </assemblies>
    </compilation>

    <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID">
      <namespaces>
        <add namespace="System.Web.Mvc"/>
        <add namespace="System.Web.Mvc.Ajax"/>
        <add namespace="System.Web.Mvc.Html"/>
        <add namespace="System.Web.Routing"/>
        <add namespace="System.Linq"/>
        <add namespace="System.Collections.Generic"/>
        <add namespace="Orchard.Mvc.Html"/>
      </namespaces>
    </pages>
  </system.web>
  <system.web.extensions/>
</configuration>