var actPage = 1;
  
  function closeDiv(page) {
  	$("#subpage" + page).animate({ height: 'show', opacity: 'show' }, 'slow');
  }
            
  $(document).ready(function() {
       $('#link1').click(function () {
  	     var pageNumber = 1;
  	     if (pageNumber == actPage) return false;
  	     var oldActPage = actPage;  	 
  	     actPage = pageNumber;
  	     $("#subpage" + oldActPage).animate({ height: 'hide', opacity: 'hide' }, 'slow', function() {closeDiv(actPage);});
         $("#link" + oldActPage).removeClass("menu_selected");
         $("#link" + actPage).addClass("menu_selected");
      });

       $('#link2').click(function () { 
  	     var pageNumber = 2;
  	     if (pageNumber == actPage) return false;       
  	     var oldActPage = actPage;      
  	     actPage = pageNumber;
  	     $("#subpage" + oldActPage).animate({ height: 'hide', opacity: 'hide' }, 'slow', function() {closeDiv(actPage);});
         $("#link" + oldActPage).removeClass("menu_selected");
         $("#link" + actPage).addClass("menu_selected");         
      });      
      
       $('#link3').click(function () { 
  	     var pageNumber = 3;
  	     if (pageNumber == actPage) return false;       
  	     var oldActPage = actPage;      
  	     actPage = pageNumber;
  	     $("#subpage" + oldActPage).animate({ height: 'hide', opacity: 'hide' }, 'slow', function() {closeDiv(actPage);});
         $("#link" + oldActPage).removeClass("menu_selected");
         $("#link" + actPage).addClass("menu_selected");         
      });        
      
       $('#link4').click(function () { 
  	     var pageNumber = 4;
  	     if (pageNumber == actPage) return false;       
  	     var oldActPage = actPage;       
  	     actPage = pageNumber;
  	     $("#subpage" + oldActPage).animate({ height: 'hide', opacity: 'hide' }, 'slow', function() {closeDiv(actPage);});
         $("#link" + oldActPage).removeClass("menu_selected");
         $("#link" + actPage).addClass("menu_selected");         
      });           
  });