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)