У вашего броузера проблема в совместимости с HTML5
Godot Download: https://godotengine.org/download
All you need for this one is the engine. Not much has actually changed in terms of the export process from Godot 2.1, but what I mention at the end regarding the Windows export does apply to all exports. Make sure that if Godot creates a file when it exports your project application, that you keep those files together!