To maximize the flexibility, Mozilla introduces a new technology called "Configurable Chrome"(Refer to [http://www.mozilla.org/xpfe/ConfigChromeSpec.html Configurable Chrome] by Benjamin Smedberg <benjamin@smedbergs.us>). A XUL file can be written in such a fashion that its chrome description comes from a mixture of physical sources, either locally, remotely, or a combination of both. An end user may customize her/his configuration to pick up any of the source type from his favor chrome providers.