title: how to code and run extension in firefox
body: <p>I am new to firefox development. I have downloaded the SDK for firefox and a standalone developer version of firefox. I don't know how to enter and test my code the way we do in .net.
  I have copied <a href="http://techpatterns.com/forums/about304.html" rel="nofollow">User Agent code</a> from <a href="http://techpatterns.com/downloads/firefox/useragentswitcher.xml" rel="nofollow">this XML</a>.
  I want to add some variations in it and want to run then.</p>