I have seen many differences in the way FM Go 15 displays things in the web viewer compared to FM Go 14. Here is a simple web viewer that displays an image and a badge icon using css. In the first image it shows how it displays in Go 14, and the 2nd image shows Go 15. Go 15 does not display it correctly.
Go 14 displays the web viewer nearly identical to FM Pro. Go 15 does not.
I have also attached a sample .fmp12