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

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

var preloadFlag = false;
function preloadImages() {
  if (document.images) {
    ct_01_z_kazakh_over = newImage("images/ct_01-z_kazakh_over.gif");
    ct_01_z_Russie_over = newImage("images/ct_01-z_Russie_over.gif");
    ct_01_z_Mongol_over = newImage("images/ct_01-z_Mongol_over.gif");
    ct_01_z_Cnord_over = newImage("images/ct_01-z_Cnord_over.gif");
    ct_01_z_Couest_over = newImage("images/ct_01-z_Couest_over.gif");
    ct_01_z_Ccentre_over = newImage("images/ct_01-z_Ccentre_over.gif");
    ct_01_c_Asudest_over = newImage("images/ct_01-c_Asudest_over.gif");
    ct_01_z_Csud_over = newImage("images/ct_01-z_Csud_over.gif");
    preloadFlag = true;
  }
}