dpark = new Array("./images/topimg2.jpg","./images/topimg3.jpg","./images/topimg4.gif");
dpark2 = new Array("./images/topimg_o1.jpg","./images/topimg_o2.jpg","./images/topimg_o3.jpg");
opark = new Array();
for(i=0 ; i<dpark2.length ; i++){
opark[i] = new Image();
opark[i].src = dpark2[i];
}

function ovparkimg(num){
document.images["menu"+num].src = opark[num].src;
}

function ouparkimg(num){
document.images["menu"+num].src = dpark[num];
}