Server Error in '/CustomReports' Application.

Error info:

Failed to map the path '/'.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Failed to map the path '/'.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[InvalidOperationException: Failed to map the path '/'.]    System.Web.Configuration.ProcessHostConfigUtils.MapPathActual(String siteName, VirtualPath path) +253    System.Web.Configuration.ProcessHostMapPath.MapPathCaching(String siteID, VirtualPath path) +669    System.Web.Configuration.ProcessHostMapPath.GetPathConfigFilenameWorker(String siteID, VirtualPath path, String& directory, String& baseName) +19    System.Web.Configuration.ProcessHostMapPath.System.Web.Configuration.IConfigMapPath.GetPathConfigFilename(String siteID, String path, String& directory, String& baseName) +37    System.Web.Configuration.HostingPreferredMapPath.GetPathConfigFilename(String siteID, String path, String& directory, String& baseName) +75    System.Web.Configuration.WebConfigurationHost.GetStreamName(String configPath) +8941366    System.Configuration.Internal.DelegatingConfigHost.GetStreamName(String configPath) +13    System.Configuration.BaseConfigurationRecord.InitConfigFromFile() +154   [ConfigurationErrorsException: An error occurred loading a configuration file: Failed to map the path '/'.]    System.Configuration.ConfigurationSchemaErrors.ThrowIfErrors(Boolean ignoreLocal) +655924    System.Configuration.BaseConfigurationRecord.ThrowIfParseErrors(ConfigurationSchemaErrors schemaErrors) +31    System.Configuration.Configuration..ctor(String locationSubPath, Type typeConfigHost, Object[] hostInitConfigurationParams) +356    System.Configuration.Internal.InternalConfigConfigurationFactory.System.Configuration.Internal.IInternalConfigConfigurationFactory.Create(Type typeConfigHost, Object[] hostInitConfigurationParams) +29    System.Web.Configuration.WebConfigurationHost.OpenConfiguration(WebLevel webLevel, ConfigurationFileMap fileMap, VirtualPath path, String site, String locationSubPath, String server, String userName, String password, IntPtr tokenHandle) +775    System.Web.Configuration.WebConfigurationManager.OpenWebConfigurationImpl(WebLevel webLevel, ConfigurationFileMap fileMap, String path, String site, String locationSubPath, String server, String userName, String password, IntPtr userToken) +84    System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(String path) +36    Microsoft.Practices.CompositeWeb.Services.WebConfigModuleInfoStore.GetConfiguration(String configFilePath) +242    Microsoft.Practices.CompositeWeb.Services.WebConfigModuleInfoStore.PopulateSection(ModulesConfigurationSection section, String rootDirectory) +188    Microsoft.Practices.CompositeWeb.Services.WebConfigModuleInfoStore.GetModuleConfigurationSection() +101    Microsoft.Practices.CompositeWeb.Services.WebModuleEnumerator.EnumerateModules() +173    Microsoft.Practices.CompositeWeb.WebClientApplication.LoadModules() +240    Microsoft.Practices.CompositeWeb.WebClientApplication.Application_Start(Object sender, EventArgs e) +162

SOLUTION  STEP1 :

Right Click on Web Project, -> Properties -Web - Make sure following is set.