function menu() {
  var suffix = '_link';
  document.getElementById("nav_info" + suffix).onmouseover = function() {
    document.getElementById("nav_info").src = "/mainweb/images/icons/nav_info.gif";
  }

  document.getElementById("nav_plan" + suffix).onmouseover = function() {
    document.getElementById("nav_plan").src = "/mainweb/images/icons/nav_planung.gif";
  }

  document.getElementById("nav_news" + suffix).onmouseover = function() {
    document.getElementById("nav_news").src = "/mainweb/images/icons/nav_aktuelles.gif";
  }

  document.getElementById("nav_shop" + suffix).onmouseover = function() {
    document.getElementById("nav_shop").src = "/mainweb/images/icons/nav_shop.gif";
  }

  document.getElementById("nav_contact" + suffix).onmouseover = function() {
    document.getElementById("nav_contact").src = "/mainweb/images/icons/nav_kontakt.gif";
  }
  
    document.getElementById("nav_branchen" + suffix).onmouseover = function() {
    document.getElementById("nav_branchen").src = "/mainweb/images/icons/nav_projekte_v3.gif";
  }
}