imageArray = new Array();
  current = "";
  function load_img(name_src)
  {
    if(document.images) {
      var temp = imageArray[name_src];
      if(! temp) {
        temp = new Image();
        temp.src = name_src;
        imageArray[name_src] = temp;
      }

      return temp;
    }
  }
  function replace_img(name, name_src)
  {    
    if(document.images) {
      if(name != current) {
        document[name].src = load_img(name_src).src;
      }
    }
  }

load_img("Media/homeON.gif");
load_img("Media/agendaON.gif.gif");
load_img("Media/speakersON.gif");
load_img("Media/orgON.gif");
load_img("Media/regON.jpg");