Website won't publish

Sorry for this but my bootstrap website will not display once I have published it, giving me the error "If you are the owner of this site, make sure that you have an index.html file in your design." can someone please help ?

Thank you

I must add that I believe it was there when I created the design but I believe I renamed it, I did however change the name of one of my pages to index.html and yet it still gave me the same error