The above demands mobile browsers (namely Safari and Chrome) back-off on their normal charade of imitating fullscreen browsers, and instead report their true width to the CSS, meaning users are served what is considered a “mobile” friendly site.
This is only one part of the puzzle, however, since you will still need to scale your content in CSS accordingly.
Something like the above keeps your site running at most resolutions with minimum work. Of course, it’s still recommended you scale fonts and the like using media queries; but we’re far too lazy for that now, aren’t we?