>>Its called responsive design: https://www.ibm.com/developerworks/community/blogs/mobileblog/entry/responsive_design_for_mobile_apps?lang=en
>
>Thanks, so basically, the backend generates a solo Web page which includes capability to be reendered differently based on the device.
>
>I see many using this approach now instead of building an app. Is app about to be deprecated? I would have assumed many big Web sites should have offered an app by now. But, based on what I see, this does not seem to be the case. They prefer to generate HTML as is.

AFAIK, Its all done with CSS....