if that's a wordpress site, look at what plugins they use - read the source code or use ScanWP.net or something.
Wonderful suggestion, but didn't see wordpress plugin related to it.There are a bunch of free jquery plugins that do this.
Just one I quickly searched for (never used it):
https://www.jqueryscript.net/other/Small-Animated-jQuery-Notification-Popup-Plugin-Notifier.html
Just search for jquery notifier or something like that.
.whateveryourelementis{
position:fixed;
bottom:0;
left:0;
width:somefixedwidthpx;
height:somefixedheightpx!
display:block;
z-index:9999;
}
Wonderful suggestion, but didn't see wordpress plugin related to it.
However, this website you shared, has a download link to download the plugin, but I can't tell how trustworthy it is.