Seems like the collapse function in "Insert code" doesn't work.

Application error log:

Event code: 3008 
Event message: A configuration error has occurred. 
Event time: 2014-10-01 13:48:25 
Event time (UTC): 2014-10-01 11:48:25 
Event ID: 5887c030f42b49eba568f05e9240f9b1 
Event sequence: 1 
Event occurrence: 1 
Event detail code: 0 
 
Application information: 
    Application domain: /LM/W3SVC/6/ROOT-7-130566377036628360 
    Trust level: Full 
    Application Virtual Path: / 
    Application Path: C:\projects\proj\proj\ 
    Machine name: machinename
 
Process information: 
    Process ID: 4052 
    Process name: w3wp.exe 
    Account name: IIS APPPOOL\proj 
 
Exception information: 
    Exception type: InvalidOperationException 
    Exception message: The pre-application start initialization method Start on type WebMatrix.WebData.PreApplicationStartCode threw an exception with the following error message: Exception has been thrown by the target of an invocation. (C:\projects\proj\proj\web.config line 187).
   at System.Web.Compilation.BuildManager.InvokePreStartInitMethodsCore(ICollection`1 methods, Func`1 setHostingEnvironmentCultures)
   at System.Web.Compilation.BuildManager.InvokePreStartInitMethods(ICollection`1 methods)
   at System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded)
   at System.Web.Compilation.BuildManager.ExecutePreAppStart()
   at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)

Exception has been thrown by the target of an invocation. (C:\projects\proj\proj\web.config line 187)
   at System.Web.Configuration.ProvidersHelper.InstantiateProvider(ProviderSettings providerSettings, Type providerType)
   at System.Web.Configuration.ProvidersHelper.InstantiateProviders(ProviderSettingsCollection configProviders, ProviderCollection providers, Type providerType)
   at System.Web.Security.Membership.InitializeSettings(Boolean initializeGeneralSettings, RuntimeConfig appConfig, MembershipSection settings)
   at System.Web.Security.Membership.Initialize()
   at System.Web.Security.Membership.get_Providers()
   at WebMatrix.WebData.WebSecurity.PreAppStartInit()
   at WebMatrix.WebData.PreApplicationStartCode.Start()

Exception has been thrown by the target of an invocation.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at System.Web.Configuration.ProvidersHelper.InstantiateProvider(ProviderSettings providerSettings, Type providerType)

Activation error occurred while trying to get instance of type SynchronizingUserService, key ""
   at EPiServer.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key)
   at EPiServer.ServiceLocation.ServiceLocatorImplBase.GetInstance[TService]()
   at EPiServer.Security.WindowsMembershipProvider..ctor()

StructureMap Exception Code:  207
Internal exception while creating Instance 'a0ce6497-721d-4aa5-8ecb-39df9b2dc90f' of PluginType EPiServer.Security.SynchronizingUserService.  Check the inner exception for more details.
   at StructureMap.Pipeline.ConstructorInstance.Build(Type pluginType, BuildSession session, IInstanceBuilder builder)
   at StructureMap.Pipeline.Instance.createRawObject(Type pluginType, BuildSession session)
   at StructureMap.Pipeline.Instance.Build(Type pluginType, BuildSession session)
   at StructureMap.Pipeline.ObjectBuilder.Resolve(Type pluginType, Instance instance, BuildSession session)
   at StructureMap.BuildSession.CreateInstance(Type pluginType, Instance instance)
   at StructureMap.BuildSession.CreateInstance(Type pluginType)
   at EPiServer.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key)

Activation error occurred while trying to get instance of type ServiceAccessor`1, key ""
   at EPiServer.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key)
   at EPiServer.ServiceLocation.ServiceLocatorImplBase.GetInstance[TService]()
   at EPiServer.Security.SynchronizingUserService..ctor()
   at lambda_method(Closure , IArguments )
   at StructureMap.Construction.BuilderCompiler.FuncCompiler`1.<>c__DisplayClass2.b__0(IArguments args)
   at StructureMap.Construction.InstanceBuilder.BuildInstance(IArguments args)
   at StructureMap.Pipeline.ConstructorInstance.Build(Type pluginType, BuildSession session, IInstanceBuilder builder)

StructureMap Exception Code:  202
No Default Instance defined for PluginFamily EPiServer.ServiceLocation.ServiceAccessor`1[[EPiServer.DataAccess.WindowsProviderDB, EPiServer, Version=7.14.0.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7]], EPiServer.Framework, Version=7.14.0.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7
   at StructureMap.BuildSession.<.ctor>b__0(Type t)
   at StructureMap.Util.Cache`2.get_Item(KEY key)
   at StructureMap.BuildSession.CreateInstance(Type pluginType)
   at EPiServer.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key)

 
 
Request information: 
    Request URL: http://localhost:17331/ 
    Request path: / 
    User host address: ::1 
    User:  
    Is authenticated: False 
    Authentication Type:  
    Thread account name: IIS APPPOOL\proj
 
Thread information: 
    Thread ID: 108 
    Thread account name: IIS APPPOOL\proj
    Is impersonating: False 
    Stack trace:    at System.Web.Compilation.BuildManager.InvokePreStartInitMethodsCore(ICollection`1 methods, Func`1 setHostingEnvironmentCultures)
   at System.Web.Compilation.BuildManager.InvokePreStartInitMethods(ICollection`1 methods)
   at System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded)
   at System.Web.Compilation.BuildManager.ExecutePreAppStart()
   at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)
 
 
Custom event details: 

It seems like the code in WebMatrix.WebData.PreApplicationStartCode accesses the membership provider very early in the application startup (it has probably a PreApplicationStartMethod assembly attribute). And since the WindowsMembershipProvider has dependencys that it expects from IOC container it fails to instantiate (since at this early stage the IOC container is not poulated).

I will report a bug and see if we can get rid of IOC dependency from the provider.

But for you: Do you have a nuget package WebMatrix.WebData, if so do you need it, it seems to have been replaced, see https://www.nuget.org/packages/WebMatrix.WebData/?? 

Fix is out in CMS.Core 7.15:

http://world.episerver.com/Documentation/Release-Notes/ReleaseNote/?releaseNoteId=118068