How to replace missing root and intermediate certificates in Mac OS X v10.8
One should never delete a Root Certificate.

And you should never delete a Root Certificate that has been Marked as Invalid before its expiration Date has been reached.

There was a reason why it was marked as invalid.

Mostly because the Issuer of the Certificate mark it as invalid (this could have been done because he got hacked or whatever could have compromised his Root Certificate).

Now you/your Browser don't have the Root Certificate so you/your Browser aren't able to validate any Certificate which is trusted by this Root.

So it depends on the Browser and how it handles Certificates of a Root it doesn't know.

If the Browser acts correct he will show you each Certificate based on this Root as invalid but some Browsers (at least in Past) didn't handle this correct and would have shown Certificates without a Root they know as valid.