As far as I can tell web services returning json is the standard way to separate business functionality and UI. also, bootstrap is a pretty common library that allows your webpages to respond to different size browsers pretty easily. After that you get into choices that are language dependent. Angular JS, knockoutjs, react others are frameworks(using loosely) in the browser. There are a lot of MVC frameworks for the Server including java based ones(groovy/grails). Then, for native you need to decide whether you might want a mobile platform that can be used for both iOS and Android. Cordova, Corona, Titanium, Xamarin.