tiphysmenu = function(nav_id) {
	toggleDisplay = function(e) {
		el = this.getElementsByTagName('ul');
		if (el.length > 0) {
			el[0].style.display = (el[0].style.display == 'block') ? 'none' : 'block';
		}
	};		
	navItems = document.getElementById(nav_id).children;
	for (i=0; i<navItems.length; i++) {
		navItems[i].onmouseover = toggleDisplay;
		navItems[i].onmouseout = toggleDisplay;
	}		
};