Question: In Firefox there is a menu item that displays "Page Source": View | Page Source (Ctrl+U).
In Internet Explorer there is a similar function.

When you invoke it, it displays a nicely formatted and syntax-highlighted collection of HTML (and JavaScript) code.

What I don't know is whether this HTML (viewable in the Page Source) is the result of *pre-processing* of the JavaScript (resulting in modification of the original raw HTML) or just *raw* as received by HTTP GET.

Answer: 
The "View Source" code is the code **before** any JavaScript is applied. 

Firefox's Web Dev toolbar will allow you to view the resulting post-JavaScript source code from the View Source > View Generated Source menu option.
It is the source that was returned to the browser by the server, before DOM updates made through javascript.