function initTooltips () {
	
	var tip = $("navtooltip");

	if (tip) {
		
		$$("#topnav a").invoke("observe","mouseover",function(event) {
			
			tip.show();
			
			var el = $(Event.element(event));
			var title = el.readAttribute('tooltip');
			var w_src = el.offsetWidth;
			var h_src = el.offsetHeight;
			var x_src = el.cumulativeOffset().left;
			var y_src = el.cumulativeOffset().top;
			var w_tip = tip.offsetWidth;
			var h_tip = tip.offsetHeight;
			var x_tip = x_src - (w_tip / 2) + (w_src / 2);
			var y_tip = y_src-h_tip+12;
			
			tip.setStyle({left:x_tip+'px',top:y_tip+'px'});
			tip.update(title);
			
			
		});
		
		$$("#topnav a").invoke("observe","mouseout",function(event) {
			tip.hide();
		});
	
	}
	
}