Since github has chosen not to support the subdomain www. in the site they provisioned for you, that URL is invalid and the webserver behind the scenes doesn't know what files to serve to that address. https and www are separate parts of a URL. http is the protocol while www is part of the domain. Historically, “www” was used to distinguish web services from other services (like FTP or mail) hosted on the same domain. For example, www.example.com might have been the web service, while ftp.example.com could have been the file transfer service. https://www.linkedin.com/feed/ and https://linkedin.com/feed/ are both valid URLs and point to the same web service.