If you install the Web Developer toolbar extension for FF, you can choose "Web Developer" -> "View Source" -> "View Generated Source" to see the source in it's current state. Web Developer also comes with DOM Inspector, giving you full access to every object and property live in the DOM.
You can also use the Firebug extension, which is awsome for debugging, to see the source and edit it live in a tree-like view, or as plain text. Firebug includes tons of useful other utilities, like a JavaScript debugger and traffic analyzer.