^ index.html is just index.html (the screenshot is showing with file extensions on) so renaming it to index.html would be index.html.html
Viewing post in Another HTML issue? Can't upload zip game
What are you talking about? You have one html showing and this is named MadBreak.html. Did you try renaming it index.html as the error message demanded?
And any dev or user that is using the hide file extension "feature" of windows should think again and deactivate it hard and forever. This feature should never have been implemented and should be default off and deinstalled. This is responsible for so much anguish, errors and virus spread, it is sickening.