//グローバルメニューの数
var preimg = new Array(6);
//左メニューの数（変数化）

for (i=1;i<7;i++){
  preimg[i] = new Image;
  preimg[i].src = "img/menu"+(i)+"_ro.gif";
}


function chimg(over){
img1 = new Image;
img1.src = "img/"+over+"_ro.gif";
document.images[over].src = img1.src;
return true;
}

function bkimg(out){
img2 = new Image;
img2.src = "img/"+out+".gif";
document.images[out].src = img2.src;
return true;
}