This is a statuscode page (InternalServerError).
        System.MissingMethodException: Constructor on type 'Mammoet.Web.Business.Handler.RobotsTxtHandler' not found.
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
   at System.Web.HttpRuntime.CreateNonPublicInstance(Type type, Object[] args)
   at System.Web.Configuration.HandlerFactoryCache..ctor(String type)
   at System.Web.HttpApplication.GetFactory(String type)
   at System.Web.HttpApplication.MaterializeHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.<>c__DisplayClass285_0.<ExecuteStepImpl>b__0()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)