I was looking for a way to display the posts within a page using a reverse order (starting from the first post).
There's a 2 years-old plugin that change the order but it's quite old (so I haven't even bothered tried it) and the plugin affects everything.
So in order to achieve what I was looking for, I've done the following change :
> file : theme-functions.php
> line : 980
> before : query_posts($cat.$tags.'showposts='.$numposts.'&caller_get_posts=1');
> after : query_posts($cat.$tags.'showposts='.$numposts.'&caller_get_posts=1'.'&&order=ASC');