It works with Firefox (just had a small problem with copy and paste that's why I switched to Vivaldi) and it should work for Chrome. Vivaldi is a Chromium, so it's nearly identical for this purpose.
What's possible is that when you copy from the spoiler that you will end up with 3 lines instead of 2.
This is the first command
var myImage = new OpenLayers.Layer.Image('myImage', 'https://openxcom.org/forum/index.php?action=dlattach;topic=9554.0;attach=53436;image', new OpenLayers.Bounds(-180, -88.759, 180, 88.759), new OpenLayers.Size(288, 144),);
The link to the openxcom forum is the link to the image.
and this is the second
map.addLayer(myImage);
Note: I have changed the name from marsterra to myImage.