function show_card(id){
   hide_all_cards();
   vis_elements(false);   
   var card = document.getElementById('student_'+id);
   if (card) {
      card.style.display='block';
   }
   return false;   
}

function hide_all_cards() {
   var container = document.getElementById('student_container');
   if (container) {
      if (container.childNodes.length) {
         for (var i=0;i<container.childNodes.length;i++) {
            if (container.childNodes[i].className=='box_pop') {
               container.childNodes[i].style.display='none';
            }
         }         
      }
   }  
   vis_elements(true);   
   return false;  
}