Simple, Semantic, Script free, Accessible Navigation pattern.
The navigation sits at the bottom of your document with an id of "#main-naviagtion".
In the header you place a 'jump to link' with a href of "#main-naviagtion".
When triggered the navigation is positioned at the top of the viewport and slides into position using CSS transitions.
Within the navigation element there's another 'jump to link' - this one has a blank href of "#" which triggers the navigation to close.
Works perfectly in all modern browsers and IE9+.
In browsers that don't support :target or css transitions it degrades to a simple jump menu.