function horizontal() {
    var navItems = document.getElementById("menu_dropdown").getElementsByTagName("li");
      
      for (var i=0; i< navItems.length; i++) {
      if(navItems[i].className == "submenu")
      {
         if(navItems[i].getElementsByTagName('ul')[0] != null)
         {
            navItems[i].onmouseover=function() {
            this.getElementsByTagName('ul')[0].style.display="block";
            	if(this.id=="i_inf" || this.id=="i_serv"){
            		document.getElementById('categoria').style.display="none";
           		}
            }            
            navItems[i].onmouseout=function() {
            this.getElementsByTagName('ul')[0].style.display="none";
            	if(this.id=="i_inf" || this.id=="i_serv"){
            		document.getElementById('categoria').style.display="block";
           		}
         	}
      }
   }
 }
 }