//preload images
   buttones=new Array();
   buttones_over=new Array();
   imagepath="images/buttons/rus/";

   for(i=0;i<4;i++){
       buttones[i]=new Image();
       buttones[i].src=imagepath + "button_" + (i+1) + ".jpg";
       buttones_over[i]=new Image();
       buttones_over[i].src=imagepath + "button_" + (i+1) + "_over.jpg";  }

//menu functions

   function over(item) {
         document.getElementById("btn_img_"+item).src=buttones_over[item].src;
   }
   function out(item) {
         document.getElementById("btn_img_"+item).src=buttones[item].src;
   }