Copied off https://mail.gnome.org/archives/gnome-web-list/2012-September/msg00000.html

When you hover over a link on the navigation bar at gnome.org its gets highlighted and when you visit
a page a button like effect are present. Both features are missing from the git.gnome.org navigtion bar.

The code below implement the missing effects (and are copied from gnome.org).

#top_bar a:hover {
    background: none repeat scroll 0 0 rgba(255, 255, 255, 0.2);
}

#top_bar a:focus {
    background: none repeat scroll 0 0 rgba(255, 255, 255, 0.15);
}

#top_bar a:active, #top_bar li.current-menu-item a, #top_bar li.current-page-ancestor a {
    background: url("images/top_bar-item-bg.png") repeat-x scroll center top #1C2021;
    box-shadow: 0 -1px 0 rgba(255, 255, 255, 0.4) inset, 0 1px 3px rgba(0, 0, 0, 0.4) inset;
}