function initImages() {
  var loadImg;
  var normsrc;
  var rollsrc;
  imgs = document.getElementsByTagName("img");
  for (i = 0; i < imgs.length; i++) {
    img = imgs[i];
    if (img.className == 'rollover') {
      loadImg = new Image();
      normsrc = img.getAttribute("src");
      rollsrc = normsrc.substring(0, normsrc.length - 4) + "_rl" + normsrc.substring(normsrc.length - 4, normsrc.length);
      loadImg.src = rollsrc;
      img.onmouseover=function(){swap(this);};
      img.onmouseout=function(){swapBack(this);};
    }
  }
}

function swap(image) {
  var oldsrc = image.getAttribute("src");
  var newsrc = oldsrc.substring(0, oldsrc.length - 4) + "_rl" + oldsrc.substring(oldsrc.length - 4, oldsrc.length);
  image.setAttribute("src", newsrc);
}

function swapBack(image) {
  var oldsrc = image.getAttribute("src");
  var newsrc = oldsrc;
  if (oldsrc.substring(oldsrc.length - 7, oldsrc.length - 4) == "_rl") {
    newsrc = oldsrc.substring(0, oldsrc.length - 7) + oldsrc.substring(oldsrc.length - 4, oldsrc.length);
  }
  image.setAttribute("src",newsrc);
}

window.onload=function(){initImages();};