Warning: Prism is no longer developed by Mozilla Labs, although this documentation will still be useful to those using WebRunner (see next paragraph). There are now two alternatives: The Prism code was picked up by Matthew Gertner who started a company to continue its open source development under the name WebRunner. See his blog post at http://www.salsitasoft.com/blog/2011/02/09/prism-is-now-webr