if (document.images) {

var btn1on = new Image();
btn1on.src = "myimages/btn_hana_on.gif";
var btn1off = new Image();
btn1off.src = "myimages/btn_hana_off.gif";

var btn2on = new Image();
btn2on.src = "myimages/btn_pt_on.gif";
var btn2off = new Image();
btn2off.src = "myimages/btn_pt_off.gif";

var btn3on = new Image();
btn3on.src = "myimages/btn_us_on.gif";
var btn3off = new Image();
btn3off.src = "myimages/btn_us_off.gif";

var btn4on = new Image();
btn4on.src = "myimages/btn_au_on.gif";
var btn4off = new Image();
btn4off.src = "myimages/btn_au_off.gif";

var btn5on = new Image();
btn5on.src = "myimages/btn_wn_on.gif";
var btn5off = new Image();
btn5off.src = "myimages/btn_wn_off.gif";


}

function On(name) {
  if (document.images) {
    document.images[name].src = eval(name + 'on.src');
  }
}

function Off(name) {
  if (document.images) {
    document.images[name].src = eval(name + 'off.src');
  }
}