Steps to repro:
1. Export game (any game), even the simplest like this
2. Upload to example.com/mygame/
3. On example.com/mygame have a "what.html" file with iFrame to load the game, like
style="margin-top: 15px; margin-bottom: 15px; width:900px; height:700px;"
4. Open Firefox, navigate to example.com/mygame/what.html: All good, game loads in iFrame
5. Open Chrome, navigate to example.com/mygame/what.html: All good, game loads in iFrame
6. Open I.E., navigate to example.com/mygame/what.html:
Expected result: All good, game loads in iFrame
Actual result: "Your browser does not appear to support HTML5. Try upgrading your browser to the latest version."
The way I "architected" my game, it kind of needs to run in an iframe.