How much is a 2008 fine silver dollar certificate worth?

Answer 1

You need to be a bit more specific.

There are no US government issued silver certificates made since the suspension of the silver standard in 1964.

There may be private mints and storage companies that do provide silver certificates (for example, you place one silver dollar in storage and they give you a certificate that promises to pay one silver dollar to whoever redeems that certificate in the future. These certificates, if valid, would be worth what one silver dollar is worth (minus perhaps the fees to actually obtain physical possession of that silver dollar)

Or perhaps you are referring to a certificate of authenticity for a 2008 silver eagle. If this is just a certificate of authenticity for a 2008 dated coin, it is nearly worthless without the coin. With the coin it might add a couple of cents to a dollar to its value, but just the piece of paper itself would be worth about 2-3 cents.