Why is my ASP.NET MVC application trying to navigate to login.aspx?

Question

I have a very very simple, "Hello World" level application that I built in ASP.NET MVC 4 / Razor. It works fine in debug mode. There is no authentication; it just goes straight to Home/Index.

Now I published it to IIS. But when I view it through IIS, for some reason it's trying to load a "login.aspx" form. I have not defined any such form, not in web.config, not anywhere else in the system. And no matter what path I put in the URL, it always redirects to the non-existent login.apsx.

WHY? How do I fix it?

EDIT: Per requests by commenters, here's my Web.config:

<?xml version="1.0" encoding="utf-8"?>
<!--
  For more information on how to configure your ASP.NET application, please visit
  http://go.microsoft.com/fwlink/?LinkId=169433
  -->
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    <sectionGroup name="dotNetOpenAuth" type="DotNetOpenAuth.Configuration.DotNetOpenAuthSection, DotNetOpenAuth.Core">
      <section name="messaging" type="DotNetOpenAuth.Configuration.MessagingElement, DotNetOpenAuth.Core" requirePermission="false" allowLocation="true" />
      <section name="reporting" type="DotNetOpenAuth.Configuration.ReportingElement, DotNetOpenAuth.Core" requirePermission="false" allowLocation="true" />
      <section name="openid" type="DotNetOpenAuth.Configuration.OpenIdElement, DotNetOpenAuth.OpenId" requirePermission="false" allowLocation="true" />
      <section name="oauth" type="DotNetOpenAuth.Configuration.OAuthElement, DotNetOpenAuth.OAuth" requirePermission="false" allowLocation="true" />
    </sectionGroup>
  </configSections>
  <connectionStrings>
    <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=aspnet-AdminBackdoor-20130314103822;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\aspnet-AdminBackdoor-20130314103822.mdf" providerName="System.Data.SqlClient" />
    <add name="MyProjectEntities" connectionString="metadata=res://*/MyProjectEntities.csdl|res://*/MyProjectEntities.ssdl|res://*/MyProjectEntities.msl;provider=System.Data.SqlClient;provider connection string='data source=localhost;initial catalog=MyProject;Integrated Security=True; ;MultipleActiveResultSets=True;App=EntityFramework'" providerName="System.Data.EntityClient" />
  </connectionStrings>
  <appSettings>
    <add key="webpages:Version" value="2.0.0.0" />
    <add key="webpages:Enabled" value="false" />
    <add key="PreserveLoginUrl" value="true" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
  </appSettings>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
    <authentication mode="None">
      <!--<forms loginUrl="~/Account/Login" timeout="2880" />-->
    </authentication>
    <pages>
      <namespaces>
        <add namespace="System.Web.Helpers" />
        <add namespace="System.Web.Mvc" />
        <add namespace="System.Web.Mvc.Ajax" />
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Optimization" />
        <add namespace="System.Web.Routing" />
        <add namespace="System.Web.WebPages" />
      </namespaces>
    </pages>
  </system.web>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false" />
    <handlers>
      <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
      <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
      <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
  </system.webServer>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-1.3.0.0" newVersion="1.3.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="DotNetOpenAuth.AspNet" publicKeyToken="2780ccd10d57b246" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.2.0.0" newVersion="4.2.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="DotNetOpenAuth.Core" publicKeyToken="2780ccd10d57b246" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.2.0.0" newVersion="4.2.0.0" />
      </dependentAssembly>
    </assemblyBinding>
    <legacyHMACWarning enabled="0" />
  </runtime>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
  </entityFramework>
  <system.net>
    <defaultProxy enabled="true" />
    <settings>
      <!-- This setting causes .NET to check certificate revocation lists (CRL) 
                 before trusting HTTPS certificates.  But this setting tends to not 
                 be allowed in shared hosting environments. -->
      <!--<servicePointManager checkCertificateRevocationList="true"/>-->
    </settings>
  </system.net>
  <dotNetOpenAuth>
    <messaging>
      <untrustedWebRequest>
        <whitelistHosts>
          <!-- Uncomment to enable communication with localhost (should generally not activate in production!) -->
          <!--<add name="localhost" />-->
        </whitelistHosts>
      </untrustedWebRequest>
    </messaging>
    <!-- Allow DotNetOpenAuth to publish usage statistics to library authors to improve the library. -->
    <reporting enabled="true" />
    <openid>
      <relyingParty>
        <security requireSsl="false">
          <!-- Uncomment the trustedProviders tag if your relying party should only accept positive assertions from a closed set of OpenID Providers. -->
          <!--<trustedProviders rejectAssertionsFromUntrustedProviders="true">
                        <add endpoint="https://www.google.com/accounts/o8/ud" />
                    </trustedProviders>-->
        </security>
        <behaviors>
          <!-- The following OPTIONAL behavior allows RPs to use SREG only, but be compatible
                         with OPs that use Attribute Exchange (in various formats). -->
          <add type="DotNetOpenAuth.OpenId.RelyingParty.Behaviors.AXFetchAsSregTransform, DotNetOpenAuth.OpenId.RelyingParty" />
        </behaviors>
      </relyingParty>
    </openid>
  </dotNetOpenAuth>
  <uri>
    <!-- The uri section is necessary to turn on .NET 3.5 support for IDN (international domain names),
             which is necessary for OpenID urls with unicode characters in the domain/host name.
             It is also required to put the Uri class into RFC 3986 escaping mode, which OpenID and OAuth require. -->
    <idn enabled="All" />
    <iriParsing enabled="true" />
  </uri>
</configuration>

Answer 1

If anyone else comes upon this, there is another potential solution as described in this other SO question. Remove the WebMatrix DLLs from your bin directory.

It is possible that this problem arises if you use "Add Deployable Dependencies" from VS 2010. That includes the WebMatrix stuff, which in turn blows up your authentication under certain circumstances. In that case, remove WebMatrix from the _bin_deployableAssemblies directory, which will in turn keep it out of bin when you build or deploy.