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.
Before. The page source is the result of the GET request by the browser sans headers. If you want to view the updated content after scripts and so forth, you'll have to use a tool like Firebug or the Web Development toolbar.