synaptic package manager updating
 

while trying to get updates using synaptic package manager,it showed a warning message saying that some files are not authenticated and asked me permission to proceed.is there any way to install only authenticated upgrades?i run gutsy

Yes, go to System > Admin > Software sources and uncheck any non-authenticated repositories (as a rule, that would be anything that is not official ubuntu or medibuntu).

The "non-authenticated" part is not as bad as it sounds; it applies to any repository that does not provide a gpg key so it does not (as a rule) mean that you are receiving something that is unreliable.

how can i know which are authenticated and which are not?all the sites have a ubuntu or medibuntu word in them..