window.addEvent('domready', function() {
/* example a:  top down */
$$('#a a').each(function(el) {
//fx
var fx = new Fx.Tween(el,{
duration: 600,
link: 'cancel'
});
//css & events
el.setStyle('background-position','0px 0px').addEvents({'mouseenter': function(e) {e.stop();
fx.start('background-position','0px 100px');},'mouseleave': function(e) {e.stop();
fx.start('background-position','0px 0px');}
});
});
});