function imgMenu(imgName,swapType) {
  document[imgName].src = "images/"+imgName+swapType+".jpg";
}
function preloadImages(){
  var x;
  var big_menu_array=array("auto", "home", "life", "more");
  preload_image = new Image(25,25);
  for (x in big_menu_array){ 
    preload_image.src="images/"+big_menu_array[x]+".jpg";
    preload_image.src="images/"+big_menu_array[x]+"_select.jpg";
  }
}