window.onload = function() {
	
	$S('a.navbutton').action({
		onmouseover: function() {
			// actual mouseover action
			this.firstChild.src = this.firstChild.src.replace(/.gif/g,'_f2.gif');

		
		},
		onmouseout: function() {
			// actual mouseover action
			this.firstChild.src = this.firstChild.src.replace(/_f2.gif/g,'.gif');

		}
	});

};