As an administrator, you must have had users complaining about permission issues while trying to browse to a site or other actions within a site. When you look at the ULS logs you would normally be looking for an "access denied" error message. Additionally, you must have also observed entries similar to
[Timestamp] w3wp.exe (0x101C) 0x1380 Windows SharePoint Services General 8xfr Verbose PermissionMask check failed. asking for 0x04000000, have 0x08431061
[Timestamp] w3wp.exe (0x101C) 0x1380 Windows SharePoint Services General 8kh7 High Access denied
If you have the hexadecimal value in the ULS log for the permission mask and wish to resolve the hexadecimal code to a more meaningful value thus helping you figure out which permission or permission set is the log talking about refer to the table available at Decode the permission mask
Thanks Praveen, this message syntax link is really helpful
great - the link isnt active anymore
Maybe this will help ...