[http://developer.mozilla.org/en/XULRunner XULRunner]is a runtime environment developed by Mozilla for providing a common backend for XUL applications.XUL-based applications include Firefox, Thunderbird, Songbird Flickr Uploader, SeaMonkey, which all run off or have the ability to run from XULRunner.* I have heard of XULRunner only once, at the Mozilla Developer Days, but I have no idea how it works, so after downloading and installing, first step is to break down how the XULRunner environment works.* the sdk [http://releases.mozilla.org/pub/mozilla.org/xulrunner/releases/1.9.0.0/ download] is about 21MB~30MB depending on what platform, and once downloaded it only needs to be unzipped or untarred into an directory, I just dumped it in root, so I don't have to move around directories too much.* Surprisingly I've learned that XUL is mixture of XML files and JavaScript, stuck into a simple directory structure. + /AppName | +-+ /chrome | | | +-+ /content | | | | | +- main.xul | | | +- chrome.manifest | +-+ /defaults | | | +-+ /preferences | | | +- prefs.js | +-+ /extension | +- application.ini* the ''application.ini'' file simply sets some meta information about the application, and min and max version the application will work with* the ''chrome.manifest'' file is used to locate application resources* the ''prefs.js' tells XULRunner where is XUL application file is, to open the main window* the ''main.xul'' file is basically the application, which is written in XML