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

function MMchangeImages() {
  if (document.images && (MMpreloadFlag == true)) {
    for (var i=0; i<MMchangeImages.arguments.length; i+=2) {
      document[MMchangeImages.arguments[i]].src = MMchangeImages.arguments[i+1];
    }
  }
}

var MMpreloadFlag = false;
function MMpreloadImages() {
if (document.images) {
    top_over = MMnewImage("./images/top_over.gif");
    back_over = MMnewImage("./images/back_over.gif");
    next_over = MMnewImage("./images/next_over.gif");
    MMpreloadFlag = true;
  }
}