What is the latest stage, where a https connection can fail (i.e. the user demanding a https version gets a browser warning that the site is not secure since no https available)?
- beginning of connection, since the browser and server must establish a communication that is not available via the demanded https address? - or
- (at least in case "https" was not directly typed as the requested URL and https is demanded by the browser/addon): at the stage where the server already has made some connection, has detected the browser, and decides what to do next, what browser/device/screen size specific content version and if/what encryption is available?