Every since I started work on GraphViz2 and Graph::Easy::Marpa I was frustrated by Firefox in that it would display an SVG image in isolation by not when I used a 'img' style link to the image, i.e. from within a web page.
But googling eventually led me to a site where the author said he had better results with 'embed'.
So, I switched to embed and it worked. Chrome of course had never had such a problem.
This means I no longer have to produce 2 sets of demos…