var src_folder = "img/";

var buttons = new Array("home", "partner", "traktoren", "presse", "ueber", "kontakt");

for(var i = 0; i < buttons.length; i++ ) {

 var img_obj_norm = new Image;
 img_obj_norm.src = src_folder + "btn_" + buttons[i] + "_norm.jpg";

 var img_obj_over = new Image;
 img_obj_over.src = src_folder + "btn_" + buttons[i] + "_over.jpg";

 //var img_obj_active = new Image;
 //img_obj_active.src = src_folder + "btn_" + buttons[i] + "_active.jpg";

}