Prism makes it possible to launch web sites from the desktop and load them into a simple browser window without all of the extra features and functionality of a regular browser. This is advantageous for users because it allows them to run those sites in a separate process from their regular Firefox browser and interact with the content without any unnecessary distractions. Prism also allows web application content to be customized in some ways to make it more conducive to desktop use.

Good for helping to prevent your Gmail account from being CSRF'ed.

Hands on: Mozilla's new Prism brings web sites to the desktop