Web Part Error: A Web Part or Web Form Control on this Page cannot be displayed or imported. The type could not be found or it is not registered as safe. Correlation ID: bf1767a1-215c-f09d-b0ca-fe4f800bd7b1.

Error Details:
[UnsafeControlException: A Web Part or Web Form Control on this Page cannot be displayed or imported. The type could not be found or it is not registered as safe.]
  at Microsoft.SharePoint.WebPartPages.WebPartImporter.CreateWebPart(Boolean clearConnections)
  at Microsoft.SharePoint.WebPartPages.WebPartImporter.Import(SPWebPartManager manager, XmlReader reader, Boolean clearConnections, Uri webPartPageUri, SPWeb spWeb)
  at Microsoft.SharePoint.WebPartPages.SPWebPartManager.CompressWebPartNoSave(Boolean isClosed)