function newImage(arg) {
  if (document.images) {
    rslt = new Image();
    rslt.src = arg;
    return rslt;
  }
}

function changeImagesArray(list) {
  if (document.images && (preloadFlag == true)) {
    for (var i=0; i<list.length; i+=2) {
        document.images[list[i]].src = this[list[i+1]].src;
    }
  }
}

function changeImages() {
  changeImagesArray(changeImages.arguments);
}


var selected =''

var preloadFlag = false;
function preloadImages() {

  if (document.images) {
	explore_over = newImage("images/nav/explore_over.gif");
    track_over = newImage("images/nav/track_over.gif");
   research_over = newImage("images/nav/research_over.gif");
    nasdaq_over = newImage("images/nav/nasdaq_over.gif");

    explore_norm = newImage("images/nav/explore.gif");
    track_norm = newImage("images/nav/track.gif");
   research_norm = newImage("images/nav/research.gif");
    nasdaq_norm = newImage("images/nav/nasdaq.gif");

    preloadFlag = true;
  }
  
  resetSelected()

}

function rollover (name) {
    changeImages(name, name+'_over');
}
function rollout (name) {
    changeImages(name, name+'_norm');

    resetSelected()
}

function resetSelected() {
  if (selected != '' && selected != undefined)
  {
	changeImages (selected, selected+'_over')
  }
}