System.Configuration.ConfigurationErrorsException. Access to web.config is denied

I had a strange error, while i was accessing a site in sharepoint at my local system with some user account other than System account. i spent 2 hours on internet and collectively got so many ideas but finally doing one thing worked for me:

System.Configuration.ConfigurationErrorsException: An error occurred loading a configuration file: Access to the path 'C:\Inetpub\wwwroot\wss\VirtualDirectories\1001\web.config' is denied. (C:\Inetpub\wwwroot\wss\VirtualDirectories\1001\web.config) ---> System.UnauthorizedAccessException: Access to the path 'C:\Inetpub\wwwroot\wss\VirtualDirectories\1001\web.config' is denied. at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy) at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share) at System.Configuration.Internal.InternalConfigHost.StaticOpenStreamForRead(String streamName) at System.Configuration.Internal.InternalConfigHost.System.Configuration.Internal.IInternalConfigHost.OpenStreamForRead(String streamName, Boolean assertPermissions) at System.Configuration.Internal.InternalConfigHost.System.Configuration.Internal.IInternalConfigHost.OpenStreamForRead(String streamName) at System.Configuration.Internal.DelegatingConfigHost.OpenStreamForRead(String streamName) at System.Configuration.UpdateConfigHost.OpenStreamForRead(String streamName) at System.Configuration.BaseConfigurationRecord.InitConfigFromFile() --- End of inner exception stack trace --- at System.Configuration.ConfigurationSchemaErrors.ThrowIfErrors(Boolean ignoreLocal) at System.Configuration.BaseConfigurationRecord.ThrowIfParseErrors(ConfigurationSchemaErrors schemaErrors) at System.Configuration.Configuration..ctor(String locationSubPath, Type typeConfigHost, Object[] hostInitConfigurationParams) at System.Configuration.Internal.InternalConfigConfigurationFactory.System.Configuration.Internal.IInternalConfigConfigurationFactory.Create(Type typeConfigHost, Object[] hostInitConfigurationParams) at System.Web.Configuration.WebConfigurationHost.OpenConfiguration(WebLevel webLevel, ConfigurationFileMap fileMap, VirtualPath path, String site, String locationSubPath, String server, String userName, String password, IntPtr tokenHandle) at System.Web.Configuration.WebConfigurationManager.OpenWebConfigurationImpl(WebLevel webLevel, ConfigurationFileMap fileMap, String path, String site, String locationSubPath, String server, String userName, String password, IntPtr userToken) at System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(String path, String site) at SIAM.Triage.WebUI.ScoreSheet.SPGVScoreSheet_RowDataBound(Object sender, GridViewRowEventArgs e) at System.Web.UI.WebControls.GridView.OnRowDataBound(GridViewRowEventArgs e) at System.Web.UI.WebControls.GridView.CreateRow(Int32 rowIndex, Int32 dataSourceIndex, DataControlRowType rowType, DataControlRowState rowState, Boolean dataBind, Object dataItem, DataControlField[] fields, TableRowCollection rows, PagedDataSource pagedDataSource) at System.Web.UI.WebControls.GridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) at Microsoft.SharePoint.WebControls.SPGridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) at System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data) at System.Web.UI.WebControls.GridView.PerformDataBinding(IEnumerable data) at System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data) at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) at System.Web.UI.WebControls.DataBoundControl.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.DataBind() at System.Web.UI.WebControls.GridView.DataBind() at SIAM.Triage.WebUI.ScoreSheet.BindData()}

Go to InetMgr(iis) and give permission to Network Service and Authenticated Users for your website.