function nv(imgname, imgof) {
	if (navigator.appVersion > "3") {
		imgnum = new Image();
		if( imgof == 0 ){
			imgnum.src = "img/top/"+imgname+".jpg";
		}else if( imgof == 1 ){
			imgnum.src = "img/top/"+imgname+"_on.jpg";
		}else if( imgof == 2 ){
			imgnum.src = "img/top/"+imgname+".gif";
		}else if( imgof == 3 ){
			imgnum.src = "img/top/"+imgname+"_on.gif";
		}
		document.images[imgname].src = imgnum.src;
	}
}