The Security Log, in Microsoft Windows, is a log that contains records of login/logout activity and/or other security-related events specified by the system’s audit policy. (Wikipedia)
If you need to looking for some security log entry found in the registry and understand what is the meaning for this specific error code, an helpful online resource is Windows Security Log Events.
This web resources by Ultimate Windows Security , is an interesting collection that helps you to quickly browse and find a problem. All events are ordered by Event code and filtered for Category , subcategory and OS (Win2000, XP , Win2003 and only Vista and Win2008 ) and detailed information regarding each event (Field level details, Examples, Discuss this event).
Link : Windows Security Log Events