if(document.images) {
 var imgs = new Array();
 imgs[6] = new Image();  imgs[6].src = "images/navi_01off.gif"; 
 imgs[7] = new Image();  imgs[7].src = "images/navi_01on.gif";
 imgs[8] = new Image();  imgs[8].src = "images/navi_02off.gif";
 imgs[9] = new Image();  imgs[9].src = "images/navi_02on.gif";
 imgs[10] = new Image();  imgs[10].src = "images/navi_03off.gif";
 imgs[11] = new Image();  imgs[11].src = "images/navi_03on.gif";
 imgs[12] = new Image();  imgs[12].src = "images/navi_04off.gif"; 
 imgs[13] = new Image();  imgs[13].src = "images/navi_04on.gif";
 imgs[14] = new Image();  imgs[14].src = "images/navi_05off.gif";
 imgs[15] = new Image();  imgs[15].src = "images/navi_05on.gif";
 imgs[16] = new Image();  imgs[16].src = "images/navi_06off.gif";
 imgs[17] = new Image();  imgs[17].src = "images/navi_06on.gif";
 imgs[18] = new Image();  imgs[18].src = "images/navi_07off.gif";
 imgs[19] = new Image();  imgs[19].src = "images/navi_07on.gif";
 imgs[20] = new Image();  imgs[20].src = "images/navi_08off.gif";
 imgs[21] = new Image();  imgs[21].src = "images/navi_08on.gif";    
}

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