nav_nj = new Image();
nav_nj.src = "images/nj_buttonOver.jpg";

nav_ph = new Image();
nav_ph.src = "images/ph_buttonOver.jpg";

nav_pb = new Image();
nav_pb.src = "images/pb_buttonOver.jpg";

nav_bt = new Image();
nav_bt.src = "images/bt_buttonOver.jpg";