Yes. Once you are happy with the Promotion you built, you can preview and test it before payment. From the Publish - Pay & Publish tab, click the Test Promotion before payment button and a new browser window will open, allowing you to see how your promotion will look as a guest.
You can then check all alerts, links and messages, enter a test Sweepstakes registration or do a test play of an Instant Win Game and see how the Thank You Page appears after registering. If anything looks less than perfect, just go back to the previous tabs of the Promotion Builder, make some edits, and try then Test Promotion before payment option as many times as you wish until you're ready to go LIVE!