if (document.images) {
 img1on = new Image();
 img1on.src = "images/flag_cz_on.gif";
 img2on = new Image();
 img2on.src = "images/flag_ger_on.gif";
 img3on = new Image();
 img3on.src = "images/flag_en_on.gif";
 img4on = new Image();
 img4on.src = "images/flag_ru_on.gif";
 img1off = new Image();
 img1off.src = "images/flag_cz_off.gif";
 img2off = new Image();
 img2off.src = "images/flag_ger_off.gif";
 img3off = new Image();
 img3off.src = "images/flag_en_off.gif";
 img4off = new Image();
 img4off.src = "images/flag_ru_off.gif";
}

function imgOn(imgName) {
 if (document.images) {
  document[imgName].src = eval(imgName + "on.src");
 }
}

function imgOff(imgName) {
 if (document.images) {
  document[imgName].src = eval(imgName + "off.src");
 }
}