if (document.images) {

  nav_main1on = new Image();
  nav_main1on.src = "_img/nav_main1on.gif";
  nav_main2on = new Image();
  nav_main2on.src = "_img/nav_main2on.gif"; 
  nav_main3on = new Image();
  nav_main3on.src = "_img/nav_main3on.gif";
  nav_main4on = new Image();
  nav_main4on.src = "_img/nav_main4on.gif";
  nav_main5on = new Image();
  nav_main5on.src = "_img/nav_main5on.gif";
  nav_main6on = new Image();
  nav_main6on.src = "_img/nav_main6on.gif";
  nav_main7on = new Image();
  nav_main7on.src = "_img/nav_main7on.gif";
  
  nav_main1off = new Image();
  nav_main1off.src = "_img/nav_main1off.gif";
  nav_main2off = new Image();
  nav_main2off.src = "_img/nav_main2off.gif";
  nav_main3off = new Image();
  nav_main3off.src = "_img/nav_main3off.gif";
  nav_main4off = new Image();
  nav_main4off.src = "_img/nav_main4off.gif";
  nav_main5off = new Image();
  nav_main5off.src = "_img/nav_main5off.gif";
  nav_main6off = new Image();
  nav_main6off.src = "_img/nav_main6off.gif";
  nav_main7off = new Image();
  nav_main7off.src = "_img/nav_main7off.gif";
  
}

function changeImages() {
  if (document.images) {
    for (var i=0; i<changeImages.arguments.length; i+=2) {
      document[changeImages.arguments[i]].src = eval(changeImages.arguments[i+1] + ".src");
    }
  }
}