By default, sites you create are optimized for mobile device viewing. There may be instances, though, that you would want this option disabled so the site would load or render on browsers or devices as preferred.
To disable mobile site viewing from the site editor:
Go to the editor of the site.
Click Styling from the left pane menu.
Under Layout at the bottom of the sidebar, select "Use desktop layout for all devices" and click Done.
Click Publish on the upper right to apply the change to the site.