A method of improving functionality of a client device comprises creating resource files for customizing content from one or more particular websites or third-party servers, storing the resource files on a customization server, downloading one or more of the resource files to the client device, downloading content from the particular websites or third-party servers, and rendering a rich user interface or application to interact with the website in accordance with the downloaded resource files. In some embodiments, the client device is a mobile device such as a handheld computer or a cellular telephone having a limited display area.