nav1a = new Image();
nav1a.src = "images/mp_gruppe.gif";
nav1b = new Image();
nav1b.src = "images/mp_gruppe_hi.gif";
nav2a = new Image();
nav2a.src = "images/mp_unternehmen.gif";
nav2b = new Image();
nav2b.src = "images/mp_unternehmen_hi.gif";
nav3a = new Image();
nav3a.src = "images/mp_mitarbeiter.gif";
nav3b = new Image();
nav3b.src = "images/mp_mitarbeiter_hi.gif";
nav4a = new Image();
nav4a.src = "images/mp_standorte.gif";
nav4b = new Image();
nav4b.src = "images/mp_standorte_hi.gif";
nav5a = new Image();
nav5a.src = "images/mp_jobboerse.gif";
nav5b = new Image();
nav5b.src = "images/mp_jobboerse_hi.gif";
nav6a = new Image();
nav6a.src = "images/mp_kontakt.gif";
nav6b = new Image();
nav6b.src = "images/mp_kontakt_hi.gif";

function swap_image (target,object) {
  window.document.images[target].src = object.src;
}