When i turn my fujifilm z20fd on it says card error

Well, in this case there is a good chance that there is some problem with your card then.
In some cases, filesystem structure gets corrupt on memory cards, depending on severity you might get variety of issues. In most cases formatting the card solves the problem.

Have you tried to use the card in any other device?
Have you tried to read the card using a card reader?

It might be worth:
a. trying to format the card in camera
b. trying the current card with a different camera (to see if there indeed is a problem with the card
b. trying a different card on your camera

Hope this helps,

Raf