Modern browsers do not allow opening the HTML generated in EA 15.2 or earlier. In EA 16.x the HTML generator and templates have been upgraded to overcome that.
Just for interest, do we know how this was achieved in EA 16.x ?
It seems to me that it was achieved changing both the generator in EA and the HTML Templates. I tried, for fun, to export the EA 16 templates and import them into EA 15.2 to see if it would work, and it didn't. I can see that there were several new macro options, e.g. the breadcrumbs that waste expanded by the generator and the navigation didn't work either.
Might be possible to tweak the EA 16 templates to work in EA 15.x but making changes to the HTML templates seems to be more of a black magic craft than a skill.
Henrik