if (document.images) {
  var about_on = new Image();
  about_on.src = "/images/header/nav/about_on.gif";
  var events_on = new Image();
  events_on.src = "/images/header/nav/events_on.gif";
  var classes_on = new Image();
  classes_on.src = "/images/header/nav/classes_on.gif";
  var reviews_on = new Image();
  reviews_on.src = "/images/header/nav/reviews_on.gif";
  var documentary_on = new Image();
  documentary_on.src = "/images/header/nav/documentary_on.gif";
  var contact_on = new Image();
  contact_on.src = "/images/header/nav/contact_on.gif";

  var about_off = new Image();
  about_off.src = "/images/header/nav/about_off.gif";
  var events_off = new Image();
  events_off.src = "/images/header/nav/events_off.gif";
  var classes_off = new Image();
  classes_off.src = "/images/header/nav/classes_off.gif";
  var reviews_off = new Image();
  reviews_off.src = "/images/header/nav/reviews_off.gif";
  var documentary_off = new Image();
  documentary_off.src = "/images/header/nav/documentary_off.gif";
  var contact_off = new Image();
  contact_off.src = "/images/header/nav/contact_off.gif";
}
function rollOn(imgName) {
  if (document.images) 
    document.images[imgName].src = eval(imgName + "_on.src");
}

function rollOff(imgName) {
  if (document.images)
    document.images[imgName].src = eval(imgName + "_off.src");
}