var aryImages = new Array(30);

  //reeds geladen
  aryImages[0] = "images/publicaties.png";
  aryImages[1] = "images/lopendonderzoek.png";
  aryImages[2] = "images/werkwijze.png";
  aryImages[3] = "images/nieuws.png";
  aryImages[4] = "images/achtergrond.png";
  aryImages[5] = "images/programma.png";
  aryImages[6] = "images/organisatie.png";
  aryImages[7] = "images/vacatures.png";
  aryImages[8] = "images/home.png";
  aryImages[9] = "images/contact.png";
  aryImages[10] = "images/links.png";

  //nog te preloaden
  aryImages[20] = "images/publicaties_on.png";
  aryImages[21] = "images/lopendonderzoek_on.png";
  aryImages[22] = "images/werkwijze_on.png";
  aryImages[23] = "images/nieuws_on.png";
  aryImages[24] = "images/achtergrond_on.png";
  aryImages[25] = "images/programma_on.png";
  aryImages[26] = "images/organisatie_on.png";
  aryImages[27] = "images/vacatures_on.png";
  aryImages[28] = "images/home_on.png";
  aryImages[29] = "images/contact_on.png";
  aryImages[30] = "images/links_on.png";

  //preload functie
  for (i=20; i < 31; i++) {
    var preload = new Image();
    preload.src = aryImages[i];
  }

  //imgae swap functie
  function swap(imgIndex,name) {
    document[name].src = aryImages[imgIndex];
  }