A website will look better on mobile devices if you follow these recommendations:
When users access a site from a mobile device, Presence Builder automatically adjusts the layout and navigation of the site to fit smaller screens. It also adds links to the site that enable users to switch between a mobile and a regular site version.
If you want to switch off these automatic optimizations and show the same version of the site regardless of the device used to view it, go to the Settings tab > Advanced, and clear the Enable mobile optimizations checkbox.
If you want to see how your website might look on a mobile device, open the menu next to the Publish button and select Mobile Preview.
Note that although mobile preview shows password-protected pages without prompting you to specify a username and a password, visitors to the actual mobile site will need to give their details to access protected pages.