Blogger supports Mobile template that allows the visitor to view the blog posts in Mobile compatible blogger template. This can be done by activating Show mobile template on mobile devices. in BloggerDashboard > Template. 
When user visits the site using Mobile devices like Android, iPhone. The template automatically changes to Mobile Template. In some cases if the Template doesn't changes or the visitor wants to switch to Desktop View or Mobile View, we can add aDrop down Box that will have the Options to Select which View is to be displayed. This can be done easily by adding the below code to the HTML Widget.