if(document.images) {
 var imgs = new Array();
imgs[0] = new Image();  imgs[0].src = "http://wokasiya.com/w_photo/menu_0a.gif"; 
imgs[1] = new Image();  imgs[1].src = "http://wokasiya.com/w_photo/menu_1a.gif";
imgs[2] = new Image();  imgs[2].src = "http://wokasiya.com/w_photo/menu_2a.gif";
imgs[3] = new Image();  imgs[3].src = "http://wokasiya.com/w_photo/menu_3a.gif";
imgs[4] = new Image();  imgs[4].src = "http://wokasiya.com/w_photo/menu_4a.gif";
imgs[5] = new Image();  imgs[5].src = "http://wokasiya.com/w_photo/menu_5a.gif";
}

function chgimg(id, imgname) {
 if(document.images) {
  if(imgs[imgname]) {
    document.images[id].src = imgs[imgname].src;
  }
  else {
    document.images[id].src = imgname;
  }
 }
}