Show button only when the action is available

I'm creating a web-page editor in which you can preview the results of your progress. It has an autosave functionality so you can actually preview the page only after it has been created on the server.

For this purpose, I was thinking about showing the preview button only when the element is actually available and retrievable from the server, but I'm afraid that the user won't see it if it only appears at a certain moment of the experience.

What do you think?