When a page doesn't load, the browser can offer a "did you mean with the http or https equivalent" meaning if someone went to the http site and really it should have been https or vice versa. An enhancement to that is that the browser could do a GET/HEAD request in the background for the http or https equivalent and only present the did you mean if the http or https equivalent loads.
Please note: with widespread https adoption this is more relevant with internal intranet sites / development apps.