function preload(imgs){
 for(var i = 0; i < imgs.length; i++){
   var imgObj = new Image();
   imgObj.src = imgs[i];
 }
}
preload(["../image/bton_top_r.gif", "../image/bton_ap_r.gif", "../image/bton_map_r.gif", "../image/bton_point_r.gif", "../image/bton_qa_r.gif", "../image/bton_apinfo_r.gif", "../image/bton_rc_r.gif", "../image/bton_road_r.gif"]);