for Error in Godot: Cross-site because Same Origin Policy. Is a secury of the web browsers what when have a request in computer user for another file:// the browser blocks the import.

A solution: Try to export the HTML5 project to a server by FTP, then open in server. Example:
1. First change the Godot directory from res:// to user:// (optional step to avoid error): Godot>project>Config.Project>Application>Config>Use Custom User Dir [V] (turn enable) and change: Custom User Dir Name to: user://  
(this is for avoid the error: "No loader found for resource: res://..." in HTML5)

2. Then Godot>Project>Export>HTML5>Export Project
3. in filezilla, open the host of your SERVER.
4. in public_html create a new folder with any name you want (if is: game_folder)
5. open game_folder and in this folder, paste the HTML5 project you exported 
6. open your site: http://www.yourdomainnameserver.com/game_folder/name_game_exported.html  (of course, these names will be different for you, but is this structure folder)
7. Done!