var topNavElms = new Array('m1', 'm2', 'm3', 'm4');
var homeTopNav = null;

var subNavElms = new Array('d1', 'd2', 'd3', 'd4');
var homeSubNav = null;
var timeoutId = null;

var USE_FADE = true;
var TIMEOUT = 1000; //  milliseconds
var CROSS_FADE_DURATION = 0.5;

var ns4 = (navigator.appName == 'Netscape' && parseInt(navigator.appVersion) == 4);
var ns6 = (document.getElementById)? true : false;
var ie4 = (document.all)? true : false;

if (document.images) {
   m1on            = new Image();
   m1on.src        = "/images/m1_h.gif";
   m1off           = new Image() ;
   m1off.src       = "/images/m1.gif";

   m2on            = new Image();
   m2on.src        = "/images/m2_h.gif";
   m2off           = new Image() ;
   m2off.src       = "/images/m2.gif";

   m3on            = new Image();
   m3on.src        = "/images/m3_h.gif";
   m3off           = new Image() ;
   m3off.src       = "/images/m3.gif";

   m4on            = new Image();
   m4on.src        = "/images/m4_h.gif";
   m4off           = new Image() ;
   m4off.src       = "/images/m4.gif";
}

function is_ie() {
  var agent = navigator.userAgent.toLowerCase();
  return ((agent.indexOf("msie") != -1) && (agent.indexOf("opera") == -1));
}

function buttonOn(buttonName)
{
   if (document.images)
   {
      var btn = document[buttonName];

      if (document.all && USE_FADE == true)
      {
        btn.filters.blendTrans.Stop();
      }

      btn.src = eval(buttonName + "on.src");
   }
}

function buttonOff(buttonName)
{
   if (document.images)
   {
      if (USE_FADE == true) {
        buttonTrans(buttonName, false);
      }
      else {
        document[buttonName].src = eval(buttonName + "off.src");
      }
   }
}

// image transition function (compatibility unknown)
function buttonTrans(buttonName, turnOn)
{
  var btn = document[buttonName];

  if (document.all)
  {
    btn.style.filter = "blendTrans(duration=0)";
    btn.style.filter = "blendTrans(duration=CROSS_FADE_DURATION)";
    btn.filters.blendTrans.Apply();
  }

  if (turnOn == true)
  {
    btn.src = eval(buttonName + "on.src");
  }
  else
  {
    btn.src = eval(buttonName + "off.src");
  }

  if (document.all)
  {
    btn.filters.blendTrans.Play();
  }
}

function hideTopNav()
{
  for (i = 0; i < topNavElms.length; i++)
  {
    buttonOff(topNavElms[i]);
  }
}

function showTopNav(buttonName)
{
  hideTopNav();
  buttonOn(buttonName);
}

function show(id)
{
  var d = window.document;

  if (ns4) obj = d.id;
  if (ns6) obj = d.getElementById(id);

  if (ns4) obj.visibility = "show";
  else if (ie4) d.all[id].style.visibility = "visible";
  else if (ns6) obj.style.visibility = "visible";

  /*
  var d = window.document;
  if (d.layers)
  {
    d[id].visibility = "show";
  }
  else
  {
    d.all[id].style.visibility = "visible";
  }
  */
}

function hide(id)
{
  var d = window.document;

  if (ns4) obj = d.id;
  if (ns6) obj = d.getElementById(id);

  if (ns4) obj.visibility = "hide";
  else if (ie4) d.all[id].style.visibility = "hidden";
  else if (ns6) obj.style.visibility = "hidden";

  /*
  if (!is_ie())
  {
    d[id].visibility = "hide";
  }
  else
  {
    d.all[id].style.visibility = "hidden";
  }
  */
}

function hideSubNav()
{
  for (i = 0; i < subNavElms.length; i++)
  {
    hide(subNavElms[i]);
  }
}

function showSubNav(id)
{
  hideSubNav();
  show(id);
}

function showNav(id, buttonName)
{
  inNav();

  showTopNav(buttonName);
  showSubNav(id);
}

function hideNav()
{
  hideTopNav();
  hideSubNav();
}

function outNav()
{
  if (homeSubNav != null)
  {
    timeoutId = setTimeout("showNav(homeSubNav, homeTopNav)", TIMEOUT);
  }
  else
  {
    timeoutId = setTimeout("hideNav()", TIMEOUT);
  }
}

function inNav()
{
  if (timeoutId != null)
  {
    clearTimeout(timeoutId);
  }
}