I can't run my web application

Server Error in '/' Application. The following errors occurred while attempting to load the app. - For the app startup parameter value 'IdentitySample.Startup,Property4U___Real_Estate_2._02', the assembly 'Property4U___Real_Estate_2._02' was not found. To disable OWIN startup discovery, add the appSetting owin:AutomaticAppStartup with a value of "false" in your web.config. To specify the OWIN startup Assembly, Class, or Method, add the appSetting owin:AppStartup with the fully qualified startup class or configuration method name in your web.config.