You need to make HTML for your website so that It can be viewed in desktop computers, laptops, tablet and mobile devices. You need to manage information for different devices.

In May 2010, Ethan Marcotte’s “Responsive Web Design” helped spur a movement of building websites designed to fluidly adapt to various platforms and device sizes —you can think mobile optimized sites and tablet-specific layouts without the need for an entirely different design or special URL. So basically one design works well in different platforms and devices

One method is doing the browser detection and making different web pages which match the platform and the devices. But it is now very difficult task because you have to make number of different web pages because no of screen sizes are increasing day by day

Another method of doing the responsive html is media query. Web developers can make the CSS files which enable to behave in correct way with different screen resolutions in different devices

As the name suggests, this design technique allows a web page to respond in real time to both a users behavior (browser window size), and device platform (including orientation).