Bug with popup window
I'm using latest vivaldi snapshot with windows 10 32bit. The following page doesn't display the small popup window containing the solution to a question when clicking on a traffic light, but simply shows shortly an empty screen without any text.
http://www.schubert-verlag.de/aufgaben/xg/xg05_01.htm Popups are allowed. On all other browsers the popup works.
Currently popup windows open as new tab. That is a bug in implementation. No fix xet. But work is in progress!