1. A device comprising: one or more processors; and one or more computer readable storage media, coupled to the one or more processors, embodying computer readable instructions executable by the one or more processors to implement a method comprising: receiving a user selection of a site mode, the site mode being associated with a web application installed on an associated client device; responsive to receiving the site mode selection, requesting a start URL, wherein the start URL is ascertained from a web application file that was created from information received from a website associated with the web application; receiving web resources associated with the start URL; rendering the web resources in a web application window; receiving a user interaction with respect to the resources rendered in the web application window; responsive to the user interaction being within boundaries, associated with a website domain or subdomain and defined by the web application file, rendering user interface customization within the boundaries in the web application window; and responsive to the user interaction not being within boundaries associated with a website domain or subdomain and defined by the web application file, rendering content associated with the user interaction in a default browser different from the web application window.