Responsive web design is a great solution to our multi-screen problem, but getting into it from the print perspective is difficult. No fixed page size, no millimetres or inches, no physical constraints to fight against. Designing in pixels for Desktop and Mobile only is also the past, as more and more gadgets can open up a website. Therefore, let’s clarify some basic principles of responsive web design here to embrace the fluid web, instead of fighting it. To keep it simple we’ll focus on layouts (yes, responsive goes way deeper than that and if you want to learn more
As screen sizes become smaller, content starts to take up more vertical space and anything below will be pushed down, it’s called the flow. That might be tricky to grasp if you are used to design with pixels and points, but makes total sense when you get used to it.