var active_id = 0;
var page_timer;
function button_over(obj) {
  obj = obj.style;
  if(obj.opacity) obj.opacity = 1; 
  if(obj.filter) obj.filter = "alpha(opacity=100)";
}

function button_out(obj) {
  if(document.getElementById('box_'+active_id) !== obj) {
    obj = obj.style;
    if(obj.opacity) obj.opacity = .5; 
    if(obj.filter) obj.filter = "alpha(opacity=50)";
}}

function content_in(alpha) {
  if(alpha > 100) alpha = 100;
  obj = document.getElementById('fadewrap').style;
  if(obj.display == 'none') obj.display = 'block';
  if(obj.opacity) obj.opacity = (alpha / 100); 
  if(obj.filter) obj.filter = "alpha(opacity=" + alpha + ")";
  if(alpha < 100) page_timer = setTimeout("content_in('"+(alpha+5)+"')",100);
}

function content_out() {
  clearTimeout(page_timer);
  document.getElementById('fadewrap').style.display = 'none';
}

function change_focus(id) {
  if(id != active_id) {
    content_out();
    if(active_id > 0) {
      document.getElementById('section_'+active_id).style.display = 'none';
      for(var i = 0; notebooks[active_id].length > i; i++) document.getElementById(notebooks[active_id][i]).style.display = 'none';
    }
    var old_active = active_id;
    active_id = id;
    if(old_active > 0) { button_out(document.getElementById('box_'+old_active)); }
    button_over(document.getElementById('box_'+active_id));
    document.getElementById('section_'+active_id).style.display = 'block';
    for(var i = 0; notebooks[active_id].length > i; i++) document.getElementById(notebooks[active_id][i]).style.display = 'block';
    last_need(id);
    content_in(0);
  }
}