Element.show = function(id){
			document.getElementById(id).style.display='block';
		}
		Element.hide = function(id){
			document.getElementById(id).style.display='none';
		}		
		
		Element.visible = function(id){
			if(document.getElementById(id).style.display=='block')
				return true;
			else
				return false;
		}
		
		
		function mainMenuOnClickItem(id_of_item, id_of_submenu)
		{
		  if(Element.visible(id_of_submenu)) 
		  {
		    Element.hide(id_of_submenu); 
		    document.getElementById(id_of_item).className = '';
		  } else {
		    document.getElementById(id_of_item).className = 'activo';
		    Element.show(id_of_submenu);
		  };
		  return null;
		};
		
		function mainMenuOnClickSubItem(id_of_item, id_of_submenu)
		{
		
		  if(Element.visible(id_of_submenu)) 
		  {
		    Element.hide(id_of_submenu); 
		    $(id_of_item).className = '';
		  } else {
		    document.getElementById(id_of_item).className = 'negra';
		    Element.show(id_of_submenu);
		  };
		
		  return null;
		};