Do you think that it is possible to open a firefox window inside a opened firefox window?,yes it is possible to do that.You can do it again and again to open multiple firefox in one window.
To do this just copy the given url inside the address bar...
  • chrome://browser/content/browser.xul
Just See the screenshot in which there is a firefox inside a firefox that contains a firefox window.



Disclaimer:Everything here is for informational purpose only