Site Editor’s built-in responsive design resizes your content and images to fit different devices and screen widths: 
You can preview the site you are building as it will appear on a Desktop, Laptop, Tablet, and Phone from both the Editor and the Preview Mode in Site Editor with the help of the Device View controls: click the control to switch the View Mode.
In Edit Mode, the Device View controls are located at the top of the screen: In Preview Mode, the View controls are located at the bottom of the screen.
In both modes, Edit and Preview, you can edit the site. In Preview mode, editing is limited; you can only edit elements of the layout (text, headings, photos, buttons) from the editing menu that appears once you select the element.
There is an infinite number of ways to design a website, but some designs are much more effective than others. If you choose a theme that doesn’t port well to a mobile device, you are severely limiting the potential of your marketing campaign. In the past websites were designed almost exclusively for desktop computers, but today we need to make more of an effort to cater to all types of computing devices – or you could be missing out on a lot of revenue.
What is Responsive Web Design?
Responsive web design is a design technique with the goal of optimizing web pages to maximize the ease-of-use for the visitor. Today, people access the Internet from all sorts of devices, including desktops, smartphones, and tablets, and this presents an enormous challenge. Each of these devices has different screen sizes, resolutions, and display options.
The challenge for website designers is structuring a website in a manner that dynamically adapts to the device that is being used to access the content. The goal is to make your website as easy to read and navigate as possible – regardless of the device that the user is using to access your content. 
Why Is Responsive Web Design Important?
Why is this so important? The short answer is one word: impatience. It can be absolutely tedious scrolling around a website on your smartphone and constantly needing to resize the images and content in order to read it.
Furthermore, poor website designs won’t even display properly on some types of devices, which will aggravate and irritate the user. This is marketing suicide – the goal is to make it extremely quick and easy for a customer to make a purchase. Otherwise, you will scare away your customers and send their business to one of your competitors. 
