To browse the code on github make sure you disable greasemonkey because
it thinks a page URL terminated with .user.js is a script, when in fact
it might be the html page to show the file info.
This script requires that you have Grasemonkey installed on your Firefox,
so if you don’t have it the first step is to go to
http://www.greasespot.net/ and install it.
This script does not retrieve all your contact list, this script is made
to be simple and fast, so it will only autocomplete names that are on the
current page’s timeline or in the visible friends grid (“Following”
section at the sidebar).
To use it, just start typing @ and the first letters of the name of the
person you want to reply. If more than one person shares the beggining
letters of the name, you can either continue to type the name until they
differ or alternativelly type the Esc key to cycle through the options.
When the prediction is correct, just type Tab or the Right Arrow key.
Check the video at http://vimeo.com/2344689