function preimg() {
	var cnt = preimg.arguments.length;
	var ImgList = new Array();
	for (i =0;i<cnt+1;i++) {
		ImgList[i] = new Image();
		ImgList[i].src = preimg.arguments[i];
	}
}

function chgimg(imgName,img) {
	document.images[imgName].src = img;
}