We are currently living in the world where most of people access the web through mobile devices. Futhermore, more and more people are accessing the web primarily and even only through the mobile devices.
Mobile first is the best practice
?oding mobile first helps to simplify the web site code. A mobile-first coding means that CSS styles are applied first to the mobile devices. Styles for the larger screens are added additionally into the stylesheet via media queries.
Responsive web design gives some tools for making layouts that respond to any screen size. But mobile first is much more prospective aproach to the coding because it allows to adapt code and user experience according to modern use cases. Optimized and light stylesheet is good for bad connectivity on the go (3G or EDGE). It allows to open new opportunities to interact with touch screens directly and lead to different considerations while designing layout and functionality.