Although any website can be viewed with a mobile browser, those websites not optimized for mobile devices look a little weird, as if the regular website font size and image dimensions were decreased to fit on a mobile screen. By contrast, websites optimized for mobile devices have fonts that are readable, images that scale to the mobile device screen, and a vertical layout suitable for a mobile phone.
Building mobile web apps is done using HTML, CSS, and JavaScript. CSS controls the website appearance across devices based on the screen width. Screens with a small width, such as those on phones, are assigned one vertically-based layout, whereas screens with a larger width, like those on tablets, are assigned another, horizontally-based layout.
Because mobile web apps are accessed from the browser, and are not installed on the user’s device, these web apps can’t send push notifications (alerts) to your phone, run in the background while the browser is minimized, or communicate with other apps.
Although you can write the HTML, CSS, and JavaScript for your mobile web app from scratch, mobile web frameworks allow you to develop from a base of pre-written code, much like the frameworks for programming languages. These mobile web frameworks include a collection of generic components that are reused frequently, and allow developers to build, test, and launch websites more quickly. Twitter Bootstrap is one such mobile web framework.
