<https://w3schools.invisionzone.com/topic/53171-problem-with-blur/#comment-292863>
<http://schema.org/text>
"What happens when you click the second button is that you focus on the current browser window, causing it to go in front of the popup window. "
<https://w3schools.invisionzone.com/topic/53171-problem-with-blur/?tab=comments#comment-293006>