Firefox multi processor support

Good morning!

I have a question about multi processor support for Firefox.

The beginnig is: how is a webside build from the code transfeered on the 
computer?

I know, that a webside is build in levels:
1. Background

2. Text

3. Decoration

4. Moving content

5. Navigation regions

and so on.


Because I have invented this.

I think this can easliy transferred into multi processor code, since 
these levels are independent.

And which other parts in the browser can work independly?

Greetings
Armin