var DOM = document.getElementById;

function menu(obj) {
  if (DOM) {
    if(obj.getElementsByTagName("div")[0].style.visibility=='visible') {
      obj.getElementsByTagName("div")[0].style.visibility='hidden';
	  } else {
      obj.getElementsByTagName("div")[0].style.visibility='visible';  
	  }
  }
}

function attach_event() {
	if(document.getElementById("navi")) {
		var sub,i;
		sub = document.getElementById("navi").getElementsByTagName("div");
		for(i=0;i<sub.length;i++) {
			sub[i].parentNode.onmouseover = function() {menu(this)};
			sub[i].parentNode.onmouseout = function() {menu(this)};
			sub[i].parentNode.onfocus  = function() {menu(this)};
		}
	}
}

if(DOM) {
	window.onload = function() {
		attach_event();
	}
}