Web Part Error: A Web Part or Web Form Control on this Page cannot be displayed or imported. The type FNC.WebParts.Existing.CalenderEventDetails.CalenderEventDetails, FNC, Version=1.0.0.0, Culture=neutral, PublicKeyToken=cabb2a885b6d80f6 could not be found or it is not registered as safe.

Error Details:
[UnsafeControlException: A Web Part or Web Form Control on this Page cannot be displayed or imported. The type FNC.WebParts.Existing.CalenderEventDetails.CalenderEventDetails, FNC, Version=1.0.0.0, Culture=neutral, PublicKeyToken=cabb2a885b6d80f6 could not be found or it is not registered as safe.]
  at Microsoft.SharePoint.ApplicationRuntime.SafeControls.GetTypeFromGuid(Guid guid, Guid solutionId, String assemblyFullName, String typeFullName, Boolean throwIfNotFound)
  at Microsoft.SharePoint.WebPartPages.SPWebPartManager.CreateWebPartsFromRowSetData(Boolean onlyInitializeClosedWebParts)