define_overs_menu = function() { 
	var submenus = document.getElementById("nav").getElementsByTagName("LI"); 
	for (var i=0; i<submenus.length; i++) { 
		submenus[i].onmouseover=function() { 
			this.className+="sub_visivel"; 
		} 
		submenus[i].onmouseout=function() { 
			this.className = ""; 
		} 
	} 
} 
if (window.attachEvent) window.attachEvent("onload", define_overs_menu);