How do I put a sale or holiday hours banner across the top of my site?

Use the Promotions banner. It shows one short line on every page of your live site, above the menu, and visitors can close it. It comes with every paid plan.

Write your message (up to 140 characters; short reads best on a phone), add a link with its own label if you like, pick a color, and choose Show it now or Start on a date. You can also Take it down on a date. Times are your business's time zone.

Only one banner shows at a time: the one that started most recently. It never shows on a preview, and people who close it don't see that banner again on their device.