How does GitHub to avoid lag / blink on page loading?

Question

When I navigate into my GitHub dashboard, It look like the page is not reloaded, but only the content which changed.

So my first thought was that it is a classic ajax trick, but when I change the content of the page (change header title via the google debugger for example) that is not supposed to be reloaded (as in the ajax hypothesis), and I click to a link, my change is reset, so this part of the page is reloaded as well, BUT it doesn't blink at all, so how do they do it?

Answer 1

https://github.com/defunkt/jquery-pjax will give you all of the magic, as a jQuery plugin