if (document.images) {
  var about_us_over = new Image();
  about_us_over.src = "images/nav/about_us_over.gif";
  var about_us_off = new Image();
  about_us_off.src = "images/nav/about_us_off.gif";
  var get_involved_over = new Image();
  get_involved_over.src = "images/nav/get_involved_over.gif";
  var get_involved_off = new Image();
  get_involved_off.src = "images/nav/get_involved_off.gif";
  var events_over = new Image();
  events_over.src = "images/nav/events_over.gif";
  var events_off = new Image();
  events_off.src = "images/nav/events_off.gif";
  var contact_us_over = new Image();
  contact_us_over.src = "images/nav/contact_us_over.gif";
  var contact_us_off = new Image();
  contact_us_off.src = "images/nav/contact_us_off.gif";
  var links_over = new Image();
  links_over.src = "images/nav/links_over.gif";
  var links_off = new Image();
  links_off.src = "images/nav/links_off.gif";
}
function rollOver(imgName) {
  if (document.images) 
    document.images[imgName].src = eval(imgName + "_over.src");
}

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