function subMenu(submenu) {
  var object = submenu;

  if(document.getElementById) {
    var element = document.getElementById(object);
    var argument = document.getElementById("menu_items").getElementsByTagName("DIV");

    if(element) {
      if(element.style.display == "none") {
        for(var i=0; i<argument.length; i++) {
          argument[i].style.display = "none";
        }

        element.style.display = "block";
      } else {
        element.style.display = "none";
      }
    }
  }
}

Detect = function() {
  var agent = navigator.userAgent.toLowerCase(); 
  this._mac = agent.indexOf('mac') != -1;
  this._win = !this._mac;
  this._w3c = document.getElementById;
  this._iex = document.all;
  this._ns4 = document.layers;
}

Detect.prototype.getObject = function(name) {
  if(this._w3c) {
    return document.getElementById(name);
  } else if(this._iex) {
    return document.all[name];
  } else if(this._ns4)  {
    return this.getObjectNS4(document,name);
  }
}

Detect.prototype.getObjectNS4 = function(object, name) {
  var d = object.layers;
  var result, temp;

  for(var i=0; i<d.length; i++){
    if(d[i].id == name) {
      result = d[i];
    } else if(d[i].layers.length) {
      var temp = this.getObjectNS4(d[i],name);
    }

    if(temp) {
      result = temp;
    }
  }

  return result;
}

Detect.prototype.getStyle = function(object) {
  return (this._ns4) ? object : object.style;
}

Detect.prototype.getScrollTop = function() {
  return this._iex ? document.body.scrollTop : window.pageYOffset;
}

MenuDiv = function(name) {
  if(name) {
    this._inherit = Detect; this._inherit(name);
    this._id  = name;
    this._element  = this.getObject(this._id);
    this._css = this.getStyle(this._element);
    this._by  = this.getTop();
    return this;
  }
}

MenuDiv.prototype = new Detect();

MenuDiv.prototype.getTop = function() {
  return parseInt(this._css.top || 0);
}

MenuDiv.prototype.scrollMenu = function() {
  var ty = this._by+this.getScrollTop();
  var my = this.getTop();
	
  this._css.visibility = 'hidden';
  this._css.top = my + (ty - my) / 4;
  this._css.visibility = 'visible';
}

Subset = new Detect();

function createMenuBg(){
	Subset.menuholder = new MenuDiv('menuholder');
	menuInterval = setInterval('Subset.menuholder.scrollMenu()',50);
}