Question: When Browser completes formatting a page using CSS and HTML etc.. Where will be all the output will be stored..? Is there any virtual location where it will store..  

Can we access that content in the background..?

Answer: 
The text content will be stored in the context of the HTML structure, which is represented in memory as a mutable programming object known as the Document Object Model and accessed via reference in JavaScript to the "document" named object.
To add to austincheneys accurate summary (+1) this page explains the text nodes you content is in within the DOM he refers to: [w3C - Traversing the DOM](http://www.w3.org/community/webed/wiki/Traversing_the_DOM)

Particularly, look at the diagram halfway down the page.