function preLoad(imgs) {
	var preImg = new Array();
	for (i = 0; i < imgs.length; i++) {
		preImg[i] = new Image();
		preImg[i].src = imgs[i];
	}
}

preLoad(["img/btn/img_left_menu1_h.png","img/btn/img_left_menu2_h.png","img/btn/img_left_menu3_h.png","img/btn/img_left_menu4_h.png","img/btn/img_left_menu5_h.png","img/btn/img_left_menu6_h.png","img/btn/img_left_menu7_h.png","img/btn/img_left_menu8_h.png","img/btn/img_top_menu1_h.gif","img/btn/img_top_menu2_h.gif","img/btn/img_top_menu3_h.gif","img/btn/img_top_menu4_h.gif"]);