Weird stuff. I guess the webdev took a screenshot from some other website and it included the arrows...
You wrote "lightbox" and I read "mapbox", I thought someone implemented an image carousel by adding photos instead of map tiles in a Google Maps-esque UI (like this but with unconnected pictures: https://www.nightcity.io)
You wrote "lightbox" and I read "mapbox", I thought someone implemented an image carousel by adding photos instead of map tiles in a Google Maps-esque UI (like this but with unconnected pictures: https://www.nightcity.io)