one day banner

 one day banner  is a feature on some sites where they show a banner at or near the top of the page as a call to action for something for that day in particular, like a protest or an election.

Tantek
undefined on tantek.com for 2016-313 US Election day.
 * http://tantek.com/2016/313/t3/new-site-feature-one-day-banner-electionday
 * 2017-07-12 for the Battle for the Net campaign.

Martijn van der Ven
on vanderven.se/martijn:
 * 2017-07-12 a one day long banner action in accordance with the Battle for the Net campaign.

Google Maps
Google Maps had a Today is Election Day one day banner.