A guide's layout not only determines where the navigation menu appears on the page but also its column layout. With side navigation, the page is divided into two sections: the first column is the page navigation; the second section is one column. Side navigation is preferable because it is more responsive to mobile devices.
Responsive design is a way to design a website so that it automatically scales its content to match the screen size on whichever device it is viewed. Responsive design makes use of flexible layouts and images. When a website supports responsive design, viewers can see the content as-is without having to make adjustments to the screen.