title: Is it possible to make part of the browser transparent to display underlying desktop/windows in a web app?
body: <p>I am developing a web application (meant to run work as a rich client and able to afford requiring any (even nightly build) version of Firefox of Chromium).</p>
  
  <p>The application interface background is meant to be transparent (showing underlying windows or desktop). How can I achieve this? Following standards does not matter but would be nice.</p>
  
  <p>Primary target platform is Linux.</p>
  
  <p><strong>UPDATE</strong> <em>addressing comments and answers received to the moment of <strong>2010-07-07T01:44Z</em></strong>.</p>
  
  <p><em>Technically</em> it's nothing about code interaction and breaking the "sandbox". It's about window composition. I even think it can be implemented pretty easy in a compositive window manager without a browser even knowing of this - just replace some useless colour (for example "fuchsia" was widely used for this during Windows 9x age) with the underlying layer content.</p>
  
  <p><em>Politically</em>, this can and should be a restrictable function (like local file and webcam access, for example), which can be allowed for trusted intranet applications (local web-tech-based rich client applications seem to be a trend beginning - Firefox and Chromium implement more and more features to facilitate this) and forbidden for unknown 3-rd party websites (but this would require more complex interaction between a browser and a window manager).</p>
  
  <p><em>The reason</em> why would I like it is that I want to build a cross-platform (Linux, Windows, Mac), zero-install, fancy-looking rich client application (not meant to be served as an Internet website) with web technologies (like HTML5, CSS3 and JavaScript). I even will probably seek to use some browser-window-less tech to run it (I've heard about Mozilla Prism and XulRunner, KDE and Windows offer to use HTML for desktop widgets, Chromium is meant to offer something alike, etc.)</p>