function showTab(cid, tag, class_act_name, class_nor_name) {
  var obj = document.getElementById(cid).childNodes;
  var old_tag = "";

  for(var i=0; i<obj.length; i++) {
    if(obj[i].id) {
	  if(document.getElementById(obj[i].id).className == class_act_name) {
        old_tag = obj[i].id;
	    break;
	  }
	}
  }
  
  if(tag != old_tag) {
    document.getElementById(old_tag).className = class_nor_name;
    document.getElementById(old_tag + "_c").style.display = "none";

    document.getElementById(tag).className = class_act_name;
    document.getElementById(tag + "_c").style.display = "block";
  }
}