Hi Sarah,
If you go to Event Details > General > Event Configuration and scroll down to Hotel Accommodations, do you have it set to "Registrants can book their hotel through hotel's website?"
If so, registrants will see a link during the registration process to click on to book their rooms. When they click on this link, it will automatically open in a new tab in their browser. Therefore, to get back to the registration process, they'll just have to switch back to the other tab that they were just on.
Best,
Julia